Simplifying expressions with radical exponents
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This is the expression that needs to be simplified:
$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$
My first step is to move the negative exponent to the denominator:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$
Then multiply the denominator and add the exponents:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$
I don't know the next steps to reach the given answer of:
$frac{9}{(9-x^2)^{3/2}}$
algebra-precalculus radicals
$endgroup$
add a comment |
$begingroup$
This is the expression that needs to be simplified:
$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$
My first step is to move the negative exponent to the denominator:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$
Then multiply the denominator and add the exponents:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$
I don't know the next steps to reach the given answer of:
$frac{9}{(9-x^2)^{3/2}}$
algebra-precalculus radicals
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$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
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– MPW
Dec 29 '18 at 16:23
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53
add a comment |
$begingroup$
This is the expression that needs to be simplified:
$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$
My first step is to move the negative exponent to the denominator:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$
Then multiply the denominator and add the exponents:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$
I don't know the next steps to reach the given answer of:
$frac{9}{(9-x^2)^{3/2}}$
algebra-precalculus radicals
$endgroup$
This is the expression that needs to be simplified:
$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$
My first step is to move the negative exponent to the denominator:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$
Then multiply the denominator and add the exponents:
$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$
I don't know the next steps to reach the given answer of:
$frac{9}{(9-x^2)^{3/2}}$
algebra-precalculus radicals
algebra-precalculus radicals
asked Dec 29 '18 at 16:20
AntoninusAntoninus
33
33
$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53
add a comment |
$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53
$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23
$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$
$endgroup$
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
add a comment |
$begingroup$
Your first step is incorrect.
$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$
You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in
$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$
Instead, you can make the substitution $u = 9-x^2$:
$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$
Plugging in $u = 9-x^2$ and simplifying gives
$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$
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add a comment |
$begingroup$
Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.
$endgroup$
add a comment |
Your Answer
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$
$endgroup$
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
add a comment |
$begingroup$
Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$
$endgroup$
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
add a comment |
$begingroup$
Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$
$endgroup$
Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$
answered Dec 29 '18 at 16:30
Dr. Sonnhard GraubnerDr. Sonnhard Graubner
79.5k42867
79.5k42867
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
add a comment |
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
$endgroup$
– Antoninus
Dec 29 '18 at 16:48
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
$$frac{sqrt n}{n} = frac{1}{sqrt n}$$
$endgroup$
– KM101
Dec 29 '18 at 16:51
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
$endgroup$
– Dr. Sonnhard Graubner
Dec 29 '18 at 16:52
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
$begingroup$
Thank you, I've got it now!
$endgroup$
– Antoninus
Dec 29 '18 at 17:11
add a comment |
$begingroup$
Your first step is incorrect.
$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$
You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in
$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$
Instead, you can make the substitution $u = 9-x^2$:
$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$
Plugging in $u = 9-x^2$ and simplifying gives
$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$
$endgroup$
add a comment |
$begingroup$
Your first step is incorrect.
$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$
You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in
$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$
Instead, you can make the substitution $u = 9-x^2$:
$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$
Plugging in $u = 9-x^2$ and simplifying gives
$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$
$endgroup$
add a comment |
$begingroup$
Your first step is incorrect.
$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$
You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in
$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$
Instead, you can make the substitution $u = 9-x^2$:
$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$
Plugging in $u = 9-x^2$ and simplifying gives
$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$
$endgroup$
Your first step is incorrect.
$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$
You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in
$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$
Instead, you can make the substitution $u = 9-x^2$:
$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$
Plugging in $u = 9-x^2$ and simplifying gives
$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$
answered Dec 29 '18 at 16:49
KM101KM101
6,0861525
6,0861525
add a comment |
add a comment |
$begingroup$
Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.
$endgroup$
add a comment |
$begingroup$
Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.
$endgroup$
add a comment |
$begingroup$
Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.
$endgroup$
Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.
answered Dec 29 '18 at 19:12
Lorenz H MenkeLorenz H Menke
9611
9611
add a comment |
add a comment |
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$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23
$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53