Find the $x$ at which the local maxima of a function ocours.
$begingroup$
The function $f(x) = intlimits_{-1}^{x}t(e^t-1)(t-1)(t-2)^3(t-3)^5 dt$ has a local maxima at $x=?$
First, I differentiated $f(x)$ and found its roots.
That came out to be $x = 0,1,2,3$. Now, one of those numbers, when plugged into $f(x)$, must give the largest value compared to the others.
In our case, since we are integrating, we would need to find the $x$ that minimizes the negative area of the function that we are integrating.
By further work and analyzing the function, I figured out that the answer must be $0$ or $2.$
But, I don't know what to do next?
Any help would be appreciated.
calculus integration functions derivatives definite-integrals
$endgroup$
add a comment |
$begingroup$
The function $f(x) = intlimits_{-1}^{x}t(e^t-1)(t-1)(t-2)^3(t-3)^5 dt$ has a local maxima at $x=?$
First, I differentiated $f(x)$ and found its roots.
That came out to be $x = 0,1,2,3$. Now, one of those numbers, when plugged into $f(x)$, must give the largest value compared to the others.
In our case, since we are integrating, we would need to find the $x$ that minimizes the negative area of the function that we are integrating.
By further work and analyzing the function, I figured out that the answer must be $0$ or $2.$
But, I don't know what to do next?
Any help would be appreciated.
calculus integration functions derivatives definite-integrals
$endgroup$
$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11
add a comment |
$begingroup$
The function $f(x) = intlimits_{-1}^{x}t(e^t-1)(t-1)(t-2)^3(t-3)^5 dt$ has a local maxima at $x=?$
First, I differentiated $f(x)$ and found its roots.
That came out to be $x = 0,1,2,3$. Now, one of those numbers, when plugged into $f(x)$, must give the largest value compared to the others.
In our case, since we are integrating, we would need to find the $x$ that minimizes the negative area of the function that we are integrating.
By further work and analyzing the function, I figured out that the answer must be $0$ or $2.$
But, I don't know what to do next?
Any help would be appreciated.
calculus integration functions derivatives definite-integrals
$endgroup$
The function $f(x) = intlimits_{-1}^{x}t(e^t-1)(t-1)(t-2)^3(t-3)^5 dt$ has a local maxima at $x=?$
First, I differentiated $f(x)$ and found its roots.
That came out to be $x = 0,1,2,3$. Now, one of those numbers, when plugged into $f(x)$, must give the largest value compared to the others.
In our case, since we are integrating, we would need to find the $x$ that minimizes the negative area of the function that we are integrating.
By further work and analyzing the function, I figured out that the answer must be $0$ or $2.$
But, I don't know what to do next?
Any help would be appreciated.
calculus integration functions derivatives definite-integrals
calculus integration functions derivatives definite-integrals
edited Dec 31 '18 at 11:16
user376343
3,9834829
3,9834829
asked Dec 30 '18 at 9:49
TonyTony
1459
1459
$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11
add a comment |
$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11
$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
HINT:
The sign of $$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5$$ is $-,+,-,+$ respectively on the intervals $(-1,1),(1,2),(2,3),(3,infty).$ From this you can finish without further calculation.
$endgroup$
add a comment |
$begingroup$
You differentiated and found the roots correctly:
$$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5=0 Rightarrow \
x_0={0,1,2,3};$$
Method 1. Check the neighborhood of the critical points:
$$begin{array}{c|c|c|c}
x_0&f'(x_0-epsilon)&f'(x_0+epsilon)&text{Type of stationary point}\
hline
0&-&-&text{inflection}\
1&-&+&text{local minimum}\
2&+&-&text{local maximum}\
3&-&+&text{local minimum}\
end{array}$$
Method 2. Check the second (or higher) order derivative at the critical points:
$$begin{align}f''(0)&=0 text{(inconclusive)}\
f''(1)&=32(e-1)>0 text{(local minimum)}\
f''(2)&=0 text{(inconclusive)}\
f''(3)&=0 text{(inconclusive)}\
end{align}$$
Now you can use higher order derivative test:
$$begin{align}f'''(0)&<0 text{(strictly decreasing inflection point)}\
f'''(2)&=0, f^{(4)}(2)<0 text{(local maximum)}\
f'''(3)&=f^{(4)}(3)=f^{(5)}(3)=0, f^{(6)}(3)>0 text{(local minimum)}.end{align}$$
Note: You don't have to calculate the higher order derivatives completely, but you should focus on the corresponding factor and the resulting sign.
$endgroup$
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
HINT:
The sign of $$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5$$ is $-,+,-,+$ respectively on the intervals $(-1,1),(1,2),(2,3),(3,infty).$ From this you can finish without further calculation.
$endgroup$
add a comment |
$begingroup$
HINT:
The sign of $$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5$$ is $-,+,-,+$ respectively on the intervals $(-1,1),(1,2),(2,3),(3,infty).$ From this you can finish without further calculation.
$endgroup$
add a comment |
$begingroup$
HINT:
The sign of $$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5$$ is $-,+,-,+$ respectively on the intervals $(-1,1),(1,2),(2,3),(3,infty).$ From this you can finish without further calculation.
$endgroup$
HINT:
The sign of $$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5$$ is $-,+,-,+$ respectively on the intervals $(-1,1),(1,2),(2,3),(3,infty).$ From this you can finish without further calculation.
answered Dec 31 '18 at 11:22
user376343user376343
3,9834829
3,9834829
add a comment |
add a comment |
$begingroup$
You differentiated and found the roots correctly:
$$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5=0 Rightarrow \
x_0={0,1,2,3};$$
Method 1. Check the neighborhood of the critical points:
$$begin{array}{c|c|c|c}
x_0&f'(x_0-epsilon)&f'(x_0+epsilon)&text{Type of stationary point}\
hline
0&-&-&text{inflection}\
1&-&+&text{local minimum}\
2&+&-&text{local maximum}\
3&-&+&text{local minimum}\
end{array}$$
Method 2. Check the second (or higher) order derivative at the critical points:
$$begin{align}f''(0)&=0 text{(inconclusive)}\
f''(1)&=32(e-1)>0 text{(local minimum)}\
f''(2)&=0 text{(inconclusive)}\
f''(3)&=0 text{(inconclusive)}\
end{align}$$
Now you can use higher order derivative test:
$$begin{align}f'''(0)&<0 text{(strictly decreasing inflection point)}\
f'''(2)&=0, f^{(4)}(2)<0 text{(local maximum)}\
f'''(3)&=f^{(4)}(3)=f^{(5)}(3)=0, f^{(6)}(3)>0 text{(local minimum)}.end{align}$$
Note: You don't have to calculate the higher order derivatives completely, but you should focus on the corresponding factor and the resulting sign.
$endgroup$
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
add a comment |
$begingroup$
You differentiated and found the roots correctly:
$$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5=0 Rightarrow \
x_0={0,1,2,3};$$
Method 1. Check the neighborhood of the critical points:
$$begin{array}{c|c|c|c}
x_0&f'(x_0-epsilon)&f'(x_0+epsilon)&text{Type of stationary point}\
hline
0&-&-&text{inflection}\
1&-&+&text{local minimum}\
2&+&-&text{local maximum}\
3&-&+&text{local minimum}\
end{array}$$
Method 2. Check the second (or higher) order derivative at the critical points:
$$begin{align}f''(0)&=0 text{(inconclusive)}\
f''(1)&=32(e-1)>0 text{(local minimum)}\
f''(2)&=0 text{(inconclusive)}\
f''(3)&=0 text{(inconclusive)}\
end{align}$$
Now you can use higher order derivative test:
$$begin{align}f'''(0)&<0 text{(strictly decreasing inflection point)}\
f'''(2)&=0, f^{(4)}(2)<0 text{(local maximum)}\
f'''(3)&=f^{(4)}(3)=f^{(5)}(3)=0, f^{(6)}(3)>0 text{(local minimum)}.end{align}$$
Note: You don't have to calculate the higher order derivatives completely, but you should focus on the corresponding factor and the resulting sign.
$endgroup$
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
add a comment |
$begingroup$
You differentiated and found the roots correctly:
$$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5=0 Rightarrow \
x_0={0,1,2,3};$$
Method 1. Check the neighborhood of the critical points:
$$begin{array}{c|c|c|c}
x_0&f'(x_0-epsilon)&f'(x_0+epsilon)&text{Type of stationary point}\
hline
0&-&-&text{inflection}\
1&-&+&text{local minimum}\
2&+&-&text{local maximum}\
3&-&+&text{local minimum}\
end{array}$$
Method 2. Check the second (or higher) order derivative at the critical points:
$$begin{align}f''(0)&=0 text{(inconclusive)}\
f''(1)&=32(e-1)>0 text{(local minimum)}\
f''(2)&=0 text{(inconclusive)}\
f''(3)&=0 text{(inconclusive)}\
end{align}$$
Now you can use higher order derivative test:
$$begin{align}f'''(0)&<0 text{(strictly decreasing inflection point)}\
f'''(2)&=0, f^{(4)}(2)<0 text{(local maximum)}\
f'''(3)&=f^{(4)}(3)=f^{(5)}(3)=0, f^{(6)}(3)>0 text{(local minimum)}.end{align}$$
Note: You don't have to calculate the higher order derivatives completely, but you should focus on the corresponding factor and the resulting sign.
$endgroup$
You differentiated and found the roots correctly:
$$f^{'}(x)=x(e^x-1)(x-1)(x-2)^3(x-3)^5=0 Rightarrow \
x_0={0,1,2,3};$$
Method 1. Check the neighborhood of the critical points:
$$begin{array}{c|c|c|c}
x_0&f'(x_0-epsilon)&f'(x_0+epsilon)&text{Type of stationary point}\
hline
0&-&-&text{inflection}\
1&-&+&text{local minimum}\
2&+&-&text{local maximum}\
3&-&+&text{local minimum}\
end{array}$$
Method 2. Check the second (or higher) order derivative at the critical points:
$$begin{align}f''(0)&=0 text{(inconclusive)}\
f''(1)&=32(e-1)>0 text{(local minimum)}\
f''(2)&=0 text{(inconclusive)}\
f''(3)&=0 text{(inconclusive)}\
end{align}$$
Now you can use higher order derivative test:
$$begin{align}f'''(0)&<0 text{(strictly decreasing inflection point)}\
f'''(2)&=0, f^{(4)}(2)<0 text{(local maximum)}\
f'''(3)&=f^{(4)}(3)=f^{(5)}(3)=0, f^{(6)}(3)>0 text{(local minimum)}.end{align}$$
Note: You don't have to calculate the higher order derivatives completely, but you should focus on the corresponding factor and the resulting sign.
answered Dec 31 '18 at 16:24
farruhotafarruhota
22.5k2942
22.5k2942
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
add a comment |
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
+1 for displaying the behavior of $f'$ via nice table.
$endgroup$
– Paramanand Singh
Dec 31 '18 at 18:34
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
Thank you and Happy New 2019!
$endgroup$
– farruhota
Dec 31 '18 at 19:02
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
So, Is the answer 2?
$endgroup$
– Tony
Dec 31 '18 at 21:34
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
$begingroup$
Yes, $f(2)approx -6965.2$ is the local maximum. See WolframAlpha answer (click on approximate form).
$endgroup$
– farruhota
Jan 1 at 14:59
add a comment |
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$begingroup$
Did you actually plug in the values and compare..
$endgroup$
– Mustafa Said
Dec 30 '18 at 10:04
$begingroup$
where do i plug the values in? Do we have f(x) just in x to "plug and compare"?
$endgroup$
– Tony
Dec 30 '18 at 10:11