tentukan rumus fungsi f(x) jika diketahui sebagai berikut! f'(x) = (3x + 1) (x-1) dan f(-1) = 6

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f'(x) = (3x +1)(x -1)
f(-1)= 6
f(x) = ∫ f'(x) dx
f(x) = ∫(3x+1)(x-1) dx
f(x)= ∫ (3x² - 2x - 1 ) dx
f(x) = x³ - x² - x + c
f(-1) = 6
(-1)³ -(-1)² -(-1) + c = 6
-1 - 1 + 1 + c = 6
1 + c = 6
c = 6 - 1
c = 5
f(x)= x³ - x² - x + 5