diketahui suatu fungsi f(x) = ax+b, jika f(1)= -1 dan f(2)=2, maka nilai dari f(8) adalah… a.41 b.32 c.27 d.20 jawab dengan caranya, besok dikumpulkan

D. 20
F(1) = a+b = -1, a = -1 - b
F(2)= 2a + b = 2, 2a = 2 - b, a = (2-b)/2
(2-b)/2 = - 1 -b
2-b = -2 - 2b
2b - b = -2-2
b = -4

a = -1 -b,
a = -1 - (-4)
a = 3

F (8) = 3 (8) + (-4)
F(8) = 24 + (-4)
F(8) = 20