# Math Help - relative extrema

1. ## relative extrema

Y= 6x^3-x^4

I need to find where the intervals are increasing and decreasing and also the relative max and min. I know I have to find the derivative first which is Y'= 18x^2-4x^3. I need to set this equal to zero to find the critical values, but I'm having a little trouble here. If anyone can help I would appreciate it!!!!!! Thanks!

2. $18x^2-4x^3=2x^2(9-2x)=0$

So you have either $x=0$ or $9-2x=0$

3. so my critical values are zero and -9/2 ???