Answer:
x=5
Step-by-step explanation:
I was working on this problem also.
Maybe my version will help, too.
You need to sketch f given the information you have.
f'(x) is approximately a a cubic polynomial which means f will look like a quartic (think W)
f slopes down (negative slope) to x=2 and then slopes down again...this is a horizontal tangent.
f then slopes down to to x=5 where is has a minimum and then slopes up.
if im not wrong
