Derivative Rules of Constant, Sum, Difference Practice Test

Let $$f(x) = \frac{x^4}{4} - \frac{x^2}{2} + 5$$. For which value of $$x$$ does $$f'(x) = 0$$?

If $$f(x) = 5x^3 - 2x^2 + x - 9$$, what is $$f'(x)$$?