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December 18, 2014

December 18, 2014

Posted by **Ellen** on Friday, July 20, 2012 at 9:23pm.

- math help -
**MathMate**, Friday, July 20, 2012 at 10:09pm1. Find f'(x)=-xe^((-x^2)/2)

2. plot f'(x) and find where f'(x) crosses the x-axis.

Note that e^((-x^2)/2)>0 ∀ x∈R. Therefore the sign is determined by the factor (-x), which is >0 for x∈(-∞0) and negative for x∈ (0,+∞).

3. Knowing that x is increasing when f'(x)>0 and decreasing when f'(x)<0, can you take it from here?

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