Question

What are the extrema of `x^3-2x^2-8x`?

Answer 1

`[2+ 2sqrt(7)]/3 and [2- 2sqrt(7)]/3`

Explanation:

`f(x)=x^3 - 2x^2 - 8x`
`f'(x)= 3x^2 - 4x -8`
`3x^2 - 4x -8=0`

since this is not factorable we use the quadratic equation

`x= [2+ 2sqrt(7)]/3`