Sketch the graph of the following equation. Show steps of finding out critical numbers, intervals of increase and decrease, absolute maximum and minimum values and concavity. y=xe^{x^2}

lexi13xoxla

lexi13xoxla

Answered question

2022-08-11

Graphing using derivatives
Sketch the graph of the following equation. Show steps of finding out critical numbers, intervals of increase and decrease, absolute maximum and minimum values and concavity.
y = x e x 2
I found the first derivative which is y = ( 2 x 2 + 1 ) e x 2 and I know that in order to find min and max the zeroes for y′ must be found, but y′ doesn't have any real zeroes, and I'm confused about how to go on with solving the problem.
If someone could help me out, that would be appreciated. Thank you in advance.

Answer & Explanation

Bryant Liu

Bryant Liu

Beginner2022-08-12Added 15 answers

Step 1
If f ( x ) = x e x 2 , then f ( x ) = 2 x 2 e x 2 + e x 2 = e x 2 ( 2 x 2 + 1 ), as you have written.
Since the derivative never equals zero or is undefined across the domain, you can conclude there are no critical numbers and no relative extrema.
Step 2
Can you show that the function is always increasing by showing that f ( x ) > 0 for all x?
To determine the concavity of the function, you must now find f′′(x). Can you proceed?
Garrett Sheppard

Garrett Sheppard

Beginner2022-08-13Added 3 answers

Step 1
You have discovered that the function is increasing, because its derivative is positive, so the function has no maximum nor minimum.
Compute also lim x x e x 2 = , lim x x e x 2 = , and note there's no oblique asymptote.
Step 2
For concavity and convexity, compute the second derivative f ( x ) = 4 x e x 2 + ( 2 x 2 + 1 ) 2 x e x 2 = 2 ( 2 x 3 + 3 x ) e x 2 .
The second derivative only vanishes at 0.

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