You don't need to use the secondderivativehere. I was talking aboutzeroes, which are different.

Given , there are two zeroes such that . That's what you want to find for f'(x)/ x_1 and x_2 such that those numbers equal 0. I would suggest the quadratic formula for the easiest way.

If f'(x)=0, that means theslopeis 0. This means the graph is flat at this point and very likely is changing directions. With me so far?