N1
f'(x) = 36x - x^3 + 20
f'(-1) = -36 + 1 + 20 = -15
N2
f'(x) = (3x^2 -3)'(x + 2) + (x + 2)'(3x^2 - 3) = 6x^2 + 12x + 3x^2 - 3 = 9x^2 + 12x - 3
f'(-2) = 36 - 24 - 3 = 9