Question

Find the critical points for f(x)=x^4-8x^2-9?

Answer 1

first step
take the derivative
second step
set it equal to zero and solve

Answer 2

This is what I have 4x^3-16x=. 4x(x^2-4)= 4x(x-2)(x+2) so would the critical points be -2,0,2?

Answer 3

yup

Answer 4

thank you!

Answer 5

yw (you did it all)

Answer 6

So now that I have the critical numbers how would I find the intervals of increase and decrease?