jika diketahuibf(2)=3 dan f(-4)=-27 nilai f(-3) adalah

f(x) = ax + b

f(2) = 3
a(2) + b = 3
2a + b = 3 ...pers.1

f(-4) = -27
a(-4) + b = -27
-4a + b = -27 ...pers.2

Eliminasi b di pers.1 dan pers.2:
2a + b = 3
-4a + b = -27
____________-
6a = 30
a = 30 ÷ 6
a = 5

Substitusikan "a = 5" ke pers.1:
2a + b = 3
2(5) + b = 3
10 + b = 3
b = 3 - 10
b = -7

f(x) = ax + b
f(x) = 5x - 7

f(-3) = 5(-3) - 7
       = -15 - 7
       = -22