f(x) = 18x + 15x^2 -4x^3 on the interval [-3,4]

A) f(-3) =

f(4) =

B) find the critical points of f(x) state x and y show your work

C) State the absolute maximum and absolute minimum values of the function on the interval [-3,4]

how do i get the critical points iv found the derivative to be 18+30x-12x^2 now what do i do?