help me please. . . .!!!

f(x) = x³ + 3x² - 24x + 3

f'(x) = 3x² + 6x -24

titik stasioner
3 (x² + 2x - 8) = 0
(x + 4)(x - 2) = 0
x= -4 atau x = 2

f(-4) = 83 dan f(2) = -13