Diketahui rumus fungsif(x)=ax+b.Jika f(-1)=3 dan f(2)=18, maka nilai f(-5) adalah

f(x) = ax + b

f(-1) = 3
-a + b = 3
a = b - 3

f(2) = 18
2a + b = 18

Substitusi
2a + b = 18
2(b - 3) + b = 18
2b - 6 + b = 18
3b = 18 + 6
3b = 24
b = 8

a = b - 3
a = 8 - 3
a = 5

Rumus fungsi
f(x) = 5x + 3

f(-5) = 5(-5) + 3
= -25 + 3
= -22