tentukan f'(x) jika diketahui

a. f(x) = x³ + 2x
f'(x) = 3x² + 2

b. f(x) = 2x - x⁴ + 4
f'(x) = 2 - 4x³

c. f(x) = (2x +3)(x² + x)
f'(x) = 2(x²+x) + (x+1)(2x+3)
= 2x² + 2x + 2x² + 5x +3
= 4x² + 7x + 3