Given: f(x) = e^(-2x^2)

f'(x) evaluated as -4xe^(-2x^2)

Now, every example I've seen thus far is a polynomial function, which makes it easy to find the roots and determine what interval it's increasing or decreasing, not so here. Any tips?

- Nov 14th 2008, 10:06 AMangrynapkinIncreasing and decreasing interval, natural exponential function
Given: f(x) = e^(-2x^2)

f'(x) evaluated as -4xe^(-2x^2)

Now, every example I've seen thus far is a polynomial function, which makes it easy to find the roots and determine what interval it's increasing or decreasing, not so here. Any tips? - Nov 14th 2008, 04:05 PMmr fantastic
- Nov 14th 2008, 04:19 PMangrynapkin
mr fantastic, thank you for your reply. I've worked through the problem and studied notes a little more carefully. The second derivative test returns concave upward for all real values, which is correct according to the graph of the original function.

f"(x) = 4e^(2x^2)[(1+4x^2)]

I set 1+4x^2 to zero as my two critical points and tested away.

Not too sure how you evaluated 4xe^(2x^2) = 0

From the graph, I know it has to be zero, but algebraically I'm not quite sure how to work that out (other than the assumption it HAS to equal zero) - Nov 14th 2008, 04:39 PMmr fantastic
- Nov 14th 2008, 04:48 PMangrynapkin
Ok thanks, if something similar pops up on the final I just wanted something like that to write out.