12th grade calculus
posted by dt .
Let f(x)=[x^39x]
[]  absolute value
a. does f'(x) exist?
b. does f'(3) exist?
c. does f'(3) exist?
d. determine all extrema of f.

I will be happy to critique your thinking. Remember, you need to work on either side of x=3 here, and on either side of x=3.