diketahu f (x) = ax -b, f (2) = 7 dan f (-1) = 1 jika f(x) =11 nilai x adalah

a(-1) - b = 1 --> -a-b = 1
a(2) - b = 7 --> 2a - b = 7
eliminasi, dapat lah a = 2, b = -3
jadi f(x) = 2x+3
jika f(x) = 2x+3= 11
maka x = (11-3)/2 = 4