diketahui rumus fungsi f(x)=ax+b.jika f(-1)=3 dan f(-2)=18,nilai f(-5)...?

f(x) = ax + b
f(-1) = a (-1) + b = - a + b = 3
f(-2) = a (-2) + b = - 2a + b = 18
---------------------------------------------(-)
a = - 15
- a + b = 3
15 + b = 3
b = 3 - 15 = - 12
f(x) = - 15x - 12
f(-5) = - 15(-5) - 12 = 75 - 12 = 63