1. ## Critical Number Help

Find the critical numbers of f(x) = (x^5)(e^-8x)

Derivative is : f '(x) = 5x^4 * (e^-8x) + x^5 * (-8e^-8x)

A critical number is whenever the derivative is either undefined or equal to zero.

Thanks!

2. Originally Posted by TSizzle55
Find the critical numbers of f(x) = (x^5)(e^-8x)

Derivative is : f '(x) = 5x^4 * (e^-8x) + x^5 * (-8e^-8x)

A critical number is whenever the derivative is either undefined or equal to zero.

Thanks!
yes, first off, this is defined everywhere. to find where we can have zero, begin by factorizing

hint: $x^4e^{-8x}$ is a common term