Tentukan fungsi F, jika diketahui f'(x)=1-x, f(3)=1

F = integral f'(x)
= J (1 -x) dx
= x - 1/2x^2 + c
F(3) = 1
3 - 1/2.3^2 + c = 1
3 - 9/2 + c = 1
c = 1 -3 + 9/2
c = -2 + 9/2
c = -4/2 + 9/2
c = -5/2
F(x) = x - 1/2x^2 -5/2
atau F(x) = -1/2x^2 + x - 5/2