If f(x)=2x³+4x²-9x+8

and the derivative is f'(x)=6x²+8x-9,

how do I find the critical points if f'(x) is not factorable??

Any help will be greatly appreciated

Hi Sarah,

If you have a quadratic you can always use the general quadratic to solve for the roots, even if you can't factor the expression. If

then the roots are

Cheers,
Penny