Solution for $46x + 10y=2$ for ${ x,y} in mathbb{Z}$ [closed]
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I've searched many youtube videos to help me solve them and although I have understood the concepts (using euclidean algorithm) I can't seem to get this right. I'd would prefer the answer to have all steps and explanations along the way, thanks.
elementary-number-theory
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closed as off-topic by José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin Dec 27 '18 at 8:56
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin
If this question can be reworded to fit the rules in the help center, please edit the question.
add a comment |
$begingroup$
I've searched many youtube videos to help me solve them and although I have understood the concepts (using euclidean algorithm) I can't seem to get this right. I'd would prefer the answer to have all steps and explanations along the way, thanks.
elementary-number-theory
$endgroup$
closed as off-topic by José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin Dec 27 '18 at 8:56
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin
If this question can be reworded to fit the rules in the help center, please edit the question.
$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
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– John Omielan
Dec 26 '18 at 22:26
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@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
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– N. S.
Dec 26 '18 at 22:27
$begingroup$
@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
$endgroup$
– John Omielan
Dec 26 '18 at 22:29
add a comment |
$begingroup$
I've searched many youtube videos to help me solve them and although I have understood the concepts (using euclidean algorithm) I can't seem to get this right. I'd would prefer the answer to have all steps and explanations along the way, thanks.
elementary-number-theory
$endgroup$
I've searched many youtube videos to help me solve them and although I have understood the concepts (using euclidean algorithm) I can't seem to get this right. I'd would prefer the answer to have all steps and explanations along the way, thanks.
elementary-number-theory
elementary-number-theory
edited Dec 26 '18 at 22:31
David G. Stork
12.2k41836
12.2k41836
asked Dec 26 '18 at 22:20
Lyon-DalipsyLyon-Dalipsy
11
11
closed as off-topic by José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin Dec 27 '18 at 8:56
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin
If this question can be reworded to fit the rules in the help center, please edit the question.
closed as off-topic by José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin Dec 27 '18 at 8:56
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – José Carlos Santos, Namaste, Eevee Trainer, KReiser, Lord_Farin
If this question can be reworded to fit the rules in the help center, please edit the question.
$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
$endgroup$
– John Omielan
Dec 26 '18 at 22:26
$begingroup$
@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
$endgroup$
– N. S.
Dec 26 '18 at 22:27
$begingroup$
@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
$endgroup$
– John Omielan
Dec 26 '18 at 22:29
add a comment |
$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
$endgroup$
– John Omielan
Dec 26 '18 at 22:26
$begingroup$
@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
$endgroup$
– N. S.
Dec 26 '18 at 22:27
$begingroup$
@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
$endgroup$
– John Omielan
Dec 26 '18 at 22:29
$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
$endgroup$
– John Omielan
Dec 26 '18 at 22:26
$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
$endgroup$
– John Omielan
Dec 26 '18 at 22:26
$begingroup$
@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
$endgroup$
– N. S.
Dec 26 '18 at 22:27
$begingroup$
@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
$endgroup$
– N. S.
Dec 26 '18 at 22:27
$begingroup$
@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
$endgroup$
– John Omielan
Dec 26 '18 at 22:29
$begingroup$
@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
$endgroup$
– John Omielan
Dec 26 '18 at 22:29
add a comment |
5 Answers
5
active
oldest
votes
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This is a actually a pretty straightforward application of the euclidean algorithm. First we want to find gcd(10,46). Since 10 = 2*5 and 46 is not divisible by 5, the gcd is 2. So we know that there are integers x,y such that 46x+10y=gcd(10,46).
So we do the euclidean algorithm:
$$ 46 = 4(10)+6$$
$$ 10 = 1(6) + 4$$
$$ 6 = 1(4)+2$$
Now we reverse the steps to get our equation.
$$ 6-1(4) = 2$$
$$ 6-1(10-1(6))=2$$ Note:We replace 4 = 10-1(6) and rewrite as
$$ 2(6)-10 =2$$
$$2(46-4(10)-10 = 2$$ Here we replace 6 = 46-4(10) and rewrite as
$$(2)46-(9)10 = 2$$
Thus x =2 and y = -9.$checkmark$
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1
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This give 1 solution... You need couple more steps to get ALL solutions ;)
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– N. S.
Dec 26 '18 at 22:30
add a comment |
$begingroup$
The given equation is equivalent to $$23x+5y=1$$
We see that $$ 23(2)+5(-9)=1$$ so $x=2$ and $y=-9$ is one solution.
We notice that we may consider $$x=2+5k$$ and $$y=-9-23k$$ for $k=0, pm 1, pm 2,....$ to get all solutions to the equation.
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-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
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– Bill Dubuque
Dec 27 '18 at 1:05
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@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
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– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
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But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
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– Bill Dubuque
Dec 27 '18 at 1:41
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@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
add a comment |
$begingroup$
The fastest way consists in performing the extended Euclidean algorithm. The equation is equivalent to solving
$$23x+5y=1,$$
which is a Bézout's relation between $23$ and $5$:
begin{array}{rrrl}
r_i &x_i &y_i&q_i\
hline
23&1&0\
5&0&1&4 \
hline
3&1&-4&1 \
2 &-1&5&1\
1&color{red}2&color{red}{-9}\
hline
end{array}
so a basic solution is $;x=2,;y=-9$. Doing some arithmetic and using Gauß' lemma shows the general solution is given by
$$x=2+5k,quad y=-9-23kquad(kin bf Z).$$
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add a comment |
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Cancelling $,2,$ yields $ 23x+5y = 1iffbmodcolor{#c00} 5!:, 23xequiv 1iff x equiv dfrac{1}{23}equiv dfrac{6}3equivcolor{#c00} 2$
So $ x = color{#c00}{2+5}n Rightarrow y = dfrac{1!-!23x}5 = dfrac{-45!-!23(5n)}5 = -9!-!23n$
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Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
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– Bill Dubuque
Dec 27 '18 at 1:09
add a comment |
$begingroup$
This was the method I first learned for tackling diophantine equations in terms of $x$ and $y$. There's a nice little theorem that comes along with it.
Theorem: Given an equation of the form$$ax+by=c$$where $a,b,cinmathbb{Z}$ and $alpha,beta$ are integral values of $x, y$ respectively, the general case takes the form$$begin{align*}x & =alpha-bt\y & =beta-atend{align*}$$where $t$ can be an arbitrary integer.
The procedure, meanwhile, is repetitive. If $alpha,beta$ cannot be easily found by inspection, then divide by the smallest coefficient and split up the improper fractions if necessary. Equate the remaining fractions to an unknown variable and solve the remaining diophantine equation. If the solutions still cannot be found by inspection, repeat until you can.
I'll walk you through with this example:$$23x+5y=1$$Since five is the smallest coefficient, divide to get that$$4x+frac 35x+y=frac 15$$The remaining fractions are $tfrac 35$ and $tfrac 15$. Setting them equal to another unknown, we'll call $z$, we get$$frac 35x=frac 15+zquadimpliesquad 3x=1+5z$$Here, it's easy to see that $z=1$ and $x=2$ are integral solutions. Now that we've found our value of $x$, it's time to substitute it into the original equation to find that $y=-9$. Hence, one value for $alpha$ and $beta$ are$$begin{align*}alpha & =2\beta & =-9end{align*}$$
Therefore, by our theorem, the rest of the solutions will take the form$$begin{align*}x & color{blue}{,,=2-5t}\y & color{red}{,,=23t-9}end{align*}$$
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add a comment |
5 Answers
5
active
oldest
votes
5 Answers
5
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
This is a actually a pretty straightforward application of the euclidean algorithm. First we want to find gcd(10,46). Since 10 = 2*5 and 46 is not divisible by 5, the gcd is 2. So we know that there are integers x,y such that 46x+10y=gcd(10,46).
So we do the euclidean algorithm:
$$ 46 = 4(10)+6$$
$$ 10 = 1(6) + 4$$
$$ 6 = 1(4)+2$$
Now we reverse the steps to get our equation.
$$ 6-1(4) = 2$$
$$ 6-1(10-1(6))=2$$ Note:We replace 4 = 10-1(6) and rewrite as
$$ 2(6)-10 =2$$
$$2(46-4(10)-10 = 2$$ Here we replace 6 = 46-4(10) and rewrite as
$$(2)46-(9)10 = 2$$
Thus x =2 and y = -9.$checkmark$
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1
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
$endgroup$
– N. S.
Dec 26 '18 at 22:30
add a comment |
$begingroup$
This is a actually a pretty straightforward application of the euclidean algorithm. First we want to find gcd(10,46). Since 10 = 2*5 and 46 is not divisible by 5, the gcd is 2. So we know that there are integers x,y such that 46x+10y=gcd(10,46).
So we do the euclidean algorithm:
$$ 46 = 4(10)+6$$
$$ 10 = 1(6) + 4$$
$$ 6 = 1(4)+2$$
Now we reverse the steps to get our equation.
$$ 6-1(4) = 2$$
$$ 6-1(10-1(6))=2$$ Note:We replace 4 = 10-1(6) and rewrite as
$$ 2(6)-10 =2$$
$$2(46-4(10)-10 = 2$$ Here we replace 6 = 46-4(10) and rewrite as
$$(2)46-(9)10 = 2$$
Thus x =2 and y = -9.$checkmark$
$endgroup$
1
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
$endgroup$
– N. S.
Dec 26 '18 at 22:30
add a comment |
$begingroup$
This is a actually a pretty straightforward application of the euclidean algorithm. First we want to find gcd(10,46). Since 10 = 2*5 and 46 is not divisible by 5, the gcd is 2. So we know that there are integers x,y such that 46x+10y=gcd(10,46).
So we do the euclidean algorithm:
$$ 46 = 4(10)+6$$
$$ 10 = 1(6) + 4$$
$$ 6 = 1(4)+2$$
Now we reverse the steps to get our equation.
$$ 6-1(4) = 2$$
$$ 6-1(10-1(6))=2$$ Note:We replace 4 = 10-1(6) and rewrite as
$$ 2(6)-10 =2$$
$$2(46-4(10)-10 = 2$$ Here we replace 6 = 46-4(10) and rewrite as
$$(2)46-(9)10 = 2$$
Thus x =2 and y = -9.$checkmark$
$endgroup$
This is a actually a pretty straightforward application of the euclidean algorithm. First we want to find gcd(10,46). Since 10 = 2*5 and 46 is not divisible by 5, the gcd is 2. So we know that there are integers x,y such that 46x+10y=gcd(10,46).
So we do the euclidean algorithm:
$$ 46 = 4(10)+6$$
$$ 10 = 1(6) + 4$$
$$ 6 = 1(4)+2$$
Now we reverse the steps to get our equation.
$$ 6-1(4) = 2$$
$$ 6-1(10-1(6))=2$$ Note:We replace 4 = 10-1(6) and rewrite as
$$ 2(6)-10 =2$$
$$2(46-4(10)-10 = 2$$ Here we replace 6 = 46-4(10) and rewrite as
$$(2)46-(9)10 = 2$$
Thus x =2 and y = -9.$checkmark$
answered Dec 26 '18 at 22:29
Joel PereiraJoel Pereira
83719
83719
1
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
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– N. S.
Dec 26 '18 at 22:30
add a comment |
1
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
$endgroup$
– N. S.
Dec 26 '18 at 22:30
1
1
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
$endgroup$
– N. S.
Dec 26 '18 at 22:30
$begingroup$
This give 1 solution... You need couple more steps to get ALL solutions ;)
$endgroup$
– N. S.
Dec 26 '18 at 22:30
add a comment |
$begingroup$
The given equation is equivalent to $$23x+5y=1$$
We see that $$ 23(2)+5(-9)=1$$ so $x=2$ and $y=-9$ is one solution.
We notice that we may consider $$x=2+5k$$ and $$y=-9-23k$$ for $k=0, pm 1, pm 2,....$ to get all solutions to the equation.
$endgroup$
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
add a comment |
$begingroup$
The given equation is equivalent to $$23x+5y=1$$
We see that $$ 23(2)+5(-9)=1$$ so $x=2$ and $y=-9$ is one solution.
We notice that we may consider $$x=2+5k$$ and $$y=-9-23k$$ for $k=0, pm 1, pm 2,....$ to get all solutions to the equation.
$endgroup$
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
add a comment |
$begingroup$
The given equation is equivalent to $$23x+5y=1$$
We see that $$ 23(2)+5(-9)=1$$ so $x=2$ and $y=-9$ is one solution.
We notice that we may consider $$x=2+5k$$ and $$y=-9-23k$$ for $k=0, pm 1, pm 2,....$ to get all solutions to the equation.
$endgroup$
The given equation is equivalent to $$23x+5y=1$$
We see that $$ 23(2)+5(-9)=1$$ so $x=2$ and $y=-9$ is one solution.
We notice that we may consider $$x=2+5k$$ and $$y=-9-23k$$ for $k=0, pm 1, pm 2,....$ to get all solutions to the equation.
answered Dec 26 '18 at 22:43
Mohammad Riazi-KermaniMohammad Riazi-Kermani
41.8k42061
41.8k42061
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
add a comment |
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
-1 Everything is pulled out of a hat - that's magic not mathematics! One should explain how "we see that..." and how "we notice that..." for it to be mathematics (vs. magic).
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:05
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
@Bill Dubuque Which part of $46-45=1$ needs more explanation ? Or may be $5(23k)-23(5k)=0$ is magical?
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:35
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
But you should explain how you found that particular solution for $,x,y$ ("we see that" does not count as a mathematical explanation). You are simply stating the solution without giving any clue whatsoever how it was derived. That's not good pedagogy. Notice all the other answers do give such explanations.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:41
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
$begingroup$
@BillDubuque Agreed, I should have explained my solution. Thanks for the comment.
$endgroup$
– Mohammad Riazi-Kermani
Dec 27 '18 at 1:57
add a comment |
$begingroup$
The fastest way consists in performing the extended Euclidean algorithm. The equation is equivalent to solving
$$23x+5y=1,$$
which is a Bézout's relation between $23$ and $5$:
begin{array}{rrrl}
r_i &x_i &y_i&q_i\
hline
23&1&0\
5&0&1&4 \
hline
3&1&-4&1 \
2 &-1&5&1\
1&color{red}2&color{red}{-9}\
hline
end{array}
so a basic solution is $;x=2,;y=-9$. Doing some arithmetic and using Gauß' lemma shows the general solution is given by
$$x=2+5k,quad y=-9-23kquad(kin bf Z).$$
$endgroup$
add a comment |
$begingroup$
The fastest way consists in performing the extended Euclidean algorithm. The equation is equivalent to solving
$$23x+5y=1,$$
which is a Bézout's relation between $23$ and $5$:
begin{array}{rrrl}
r_i &x_i &y_i&q_i\
hline
23&1&0\
5&0&1&4 \
hline
3&1&-4&1 \
2 &-1&5&1\
1&color{red}2&color{red}{-9}\
hline
end{array}
so a basic solution is $;x=2,;y=-9$. Doing some arithmetic and using Gauß' lemma shows the general solution is given by
$$x=2+5k,quad y=-9-23kquad(kin bf Z).$$
$endgroup$
add a comment |
$begingroup$
The fastest way consists in performing the extended Euclidean algorithm. The equation is equivalent to solving
$$23x+5y=1,$$
which is a Bézout's relation between $23$ and $5$:
begin{array}{rrrl}
r_i &x_i &y_i&q_i\
hline
23&1&0\
5&0&1&4 \
hline
3&1&-4&1 \
2 &-1&5&1\
1&color{red}2&color{red}{-9}\
hline
end{array}
so a basic solution is $;x=2,;y=-9$. Doing some arithmetic and using Gauß' lemma shows the general solution is given by
$$x=2+5k,quad y=-9-23kquad(kin bf Z).$$
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The fastest way consists in performing the extended Euclidean algorithm. The equation is equivalent to solving
$$23x+5y=1,$$
which is a Bézout's relation between $23$ and $5$:
begin{array}{rrrl}
r_i &x_i &y_i&q_i\
hline
23&1&0\
5&0&1&4 \
hline
3&1&-4&1 \
2 &-1&5&1\
1&color{red}2&color{red}{-9}\
hline
end{array}
so a basic solution is $;x=2,;y=-9$. Doing some arithmetic and using Gauß' lemma shows the general solution is given by
$$x=2+5k,quad y=-9-23kquad(kin bf Z).$$
answered Dec 26 '18 at 22:45
BernardBernard
124k741117
124k741117
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$begingroup$
Cancelling $,2,$ yields $ 23x+5y = 1iffbmodcolor{#c00} 5!:, 23xequiv 1iff x equiv dfrac{1}{23}equiv dfrac{6}3equivcolor{#c00} 2$
So $ x = color{#c00}{2+5}n Rightarrow y = dfrac{1!-!23x}5 = dfrac{-45!-!23(5n)}5 = -9!-!23n$
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Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
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$begingroup$
Cancelling $,2,$ yields $ 23x+5y = 1iffbmodcolor{#c00} 5!:, 23xequiv 1iff x equiv dfrac{1}{23}equiv dfrac{6}3equivcolor{#c00} 2$
So $ x = color{#c00}{2+5}n Rightarrow y = dfrac{1!-!23x}5 = dfrac{-45!-!23(5n)}5 = -9!-!23n$
$endgroup$
$begingroup$
Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
add a comment |
$begingroup$
Cancelling $,2,$ yields $ 23x+5y = 1iffbmodcolor{#c00} 5!:, 23xequiv 1iff x equiv dfrac{1}{23}equiv dfrac{6}3equivcolor{#c00} 2$
So $ x = color{#c00}{2+5}n Rightarrow y = dfrac{1!-!23x}5 = dfrac{-45!-!23(5n)}5 = -9!-!23n$
$endgroup$
Cancelling $,2,$ yields $ 23x+5y = 1iffbmodcolor{#c00} 5!:, 23xequiv 1iff x equiv dfrac{1}{23}equiv dfrac{6}3equivcolor{#c00} 2$
So $ x = color{#c00}{2+5}n Rightarrow y = dfrac{1!-!23x}5 = dfrac{-45!-!23(5n)}5 = -9!-!23n$
answered Dec 27 '18 at 0:59
Bill DubuqueBill Dubuque
214k29197656
214k29197656
$begingroup$
Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
add a comment |
$begingroup$
Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
$begingroup$
Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
$begingroup$
Beware $ $ Modular fraction arithmetic is well-defined only for fractions with denominator coprime to the modulus. See here for further discussion.
$endgroup$
– Bill Dubuque
Dec 27 '18 at 1:09
add a comment |
$begingroup$
This was the method I first learned for tackling diophantine equations in terms of $x$ and $y$. There's a nice little theorem that comes along with it.
Theorem: Given an equation of the form$$ax+by=c$$where $a,b,cinmathbb{Z}$ and $alpha,beta$ are integral values of $x, y$ respectively, the general case takes the form$$begin{align*}x & =alpha-bt\y & =beta-atend{align*}$$where $t$ can be an arbitrary integer.
The procedure, meanwhile, is repetitive. If $alpha,beta$ cannot be easily found by inspection, then divide by the smallest coefficient and split up the improper fractions if necessary. Equate the remaining fractions to an unknown variable and solve the remaining diophantine equation. If the solutions still cannot be found by inspection, repeat until you can.
I'll walk you through with this example:$$23x+5y=1$$Since five is the smallest coefficient, divide to get that$$4x+frac 35x+y=frac 15$$The remaining fractions are $tfrac 35$ and $tfrac 15$. Setting them equal to another unknown, we'll call $z$, we get$$frac 35x=frac 15+zquadimpliesquad 3x=1+5z$$Here, it's easy to see that $z=1$ and $x=2$ are integral solutions. Now that we've found our value of $x$, it's time to substitute it into the original equation to find that $y=-9$. Hence, one value for $alpha$ and $beta$ are$$begin{align*}alpha & =2\beta & =-9end{align*}$$
Therefore, by our theorem, the rest of the solutions will take the form$$begin{align*}x & color{blue}{,,=2-5t}\y & color{red}{,,=23t-9}end{align*}$$
$endgroup$
add a comment |
$begingroup$
This was the method I first learned for tackling diophantine equations in terms of $x$ and $y$. There's a nice little theorem that comes along with it.
Theorem: Given an equation of the form$$ax+by=c$$where $a,b,cinmathbb{Z}$ and $alpha,beta$ are integral values of $x, y$ respectively, the general case takes the form$$begin{align*}x & =alpha-bt\y & =beta-atend{align*}$$where $t$ can be an arbitrary integer.
The procedure, meanwhile, is repetitive. If $alpha,beta$ cannot be easily found by inspection, then divide by the smallest coefficient and split up the improper fractions if necessary. Equate the remaining fractions to an unknown variable and solve the remaining diophantine equation. If the solutions still cannot be found by inspection, repeat until you can.
I'll walk you through with this example:$$23x+5y=1$$Since five is the smallest coefficient, divide to get that$$4x+frac 35x+y=frac 15$$The remaining fractions are $tfrac 35$ and $tfrac 15$. Setting them equal to another unknown, we'll call $z$, we get$$frac 35x=frac 15+zquadimpliesquad 3x=1+5z$$Here, it's easy to see that $z=1$ and $x=2$ are integral solutions. Now that we've found our value of $x$, it's time to substitute it into the original equation to find that $y=-9$. Hence, one value for $alpha$ and $beta$ are$$begin{align*}alpha & =2\beta & =-9end{align*}$$
Therefore, by our theorem, the rest of the solutions will take the form$$begin{align*}x & color{blue}{,,=2-5t}\y & color{red}{,,=23t-9}end{align*}$$
$endgroup$
add a comment |
$begingroup$
This was the method I first learned for tackling diophantine equations in terms of $x$ and $y$. There's a nice little theorem that comes along with it.
Theorem: Given an equation of the form$$ax+by=c$$where $a,b,cinmathbb{Z}$ and $alpha,beta$ are integral values of $x, y$ respectively, the general case takes the form$$begin{align*}x & =alpha-bt\y & =beta-atend{align*}$$where $t$ can be an arbitrary integer.
The procedure, meanwhile, is repetitive. If $alpha,beta$ cannot be easily found by inspection, then divide by the smallest coefficient and split up the improper fractions if necessary. Equate the remaining fractions to an unknown variable and solve the remaining diophantine equation. If the solutions still cannot be found by inspection, repeat until you can.
I'll walk you through with this example:$$23x+5y=1$$Since five is the smallest coefficient, divide to get that$$4x+frac 35x+y=frac 15$$The remaining fractions are $tfrac 35$ and $tfrac 15$. Setting them equal to another unknown, we'll call $z$, we get$$frac 35x=frac 15+zquadimpliesquad 3x=1+5z$$Here, it's easy to see that $z=1$ and $x=2$ are integral solutions. Now that we've found our value of $x$, it's time to substitute it into the original equation to find that $y=-9$. Hence, one value for $alpha$ and $beta$ are$$begin{align*}alpha & =2\beta & =-9end{align*}$$
Therefore, by our theorem, the rest of the solutions will take the form$$begin{align*}x & color{blue}{,,=2-5t}\y & color{red}{,,=23t-9}end{align*}$$
$endgroup$
This was the method I first learned for tackling diophantine equations in terms of $x$ and $y$. There's a nice little theorem that comes along with it.
Theorem: Given an equation of the form$$ax+by=c$$where $a,b,cinmathbb{Z}$ and $alpha,beta$ are integral values of $x, y$ respectively, the general case takes the form$$begin{align*}x & =alpha-bt\y & =beta-atend{align*}$$where $t$ can be an arbitrary integer.
The procedure, meanwhile, is repetitive. If $alpha,beta$ cannot be easily found by inspection, then divide by the smallest coefficient and split up the improper fractions if necessary. Equate the remaining fractions to an unknown variable and solve the remaining diophantine equation. If the solutions still cannot be found by inspection, repeat until you can.
I'll walk you through with this example:$$23x+5y=1$$Since five is the smallest coefficient, divide to get that$$4x+frac 35x+y=frac 15$$The remaining fractions are $tfrac 35$ and $tfrac 15$. Setting them equal to another unknown, we'll call $z$, we get$$frac 35x=frac 15+zquadimpliesquad 3x=1+5z$$Here, it's easy to see that $z=1$ and $x=2$ are integral solutions. Now that we've found our value of $x$, it's time to substitute it into the original equation to find that $y=-9$. Hence, one value for $alpha$ and $beta$ are$$begin{align*}alpha & =2\beta & =-9end{align*}$$
Therefore, by our theorem, the rest of the solutions will take the form$$begin{align*}x & color{blue}{,,=2-5t}\y & color{red}{,,=23t-9}end{align*}$$
answered Dec 27 '18 at 4:02
Frank W.Frank W.
3,7371321
3,7371321
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$begingroup$
Lyon-Dalipsy, welcome to MSE. When you ask for a "solution" to the equation, what do you mean? Do you mean how to determine $y$ in terms of $x$, or something else?
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– John Omielan
Dec 26 '18 at 22:26
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@JohnOmielan The number theory tag and the mention of Euclidian algorithm imply that this needs to be solved as a diophantine equation, i.e. finding all integer solutions.
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– N. S.
Dec 26 '18 at 22:27
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@N.S. Thanks for mentioning this. I am still fairly new here so I forget that the tags are not just for searching or grouping on, but they also can implicitly specify what questions are being asked.
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– John Omielan
Dec 26 '18 at 22:29