Sebuah fungsi f ( x ) = ax + b jika f ( 3 ) = – 1 dan f ( – 3 ) = – 13 maka nilai f ( 6 ) adalah…

Jawab :

f(x) = ax + b
f(3) = a(3) + b = 3a + b = -1
f(-3) = a(-3) + b = -3a + b = -13

3a + b = -1
-3a + b = -13
____________ –
6a =  12
  a = 2

-3a + b = -13
-3(2) + b = -13
-6 + b = -13
       b = -13 + 6
       b = -7

f(x) = ax + b = 2x – 7

Maka : Nilai f(6) = 2(6) – 7
                          = 12  – 7
                          = 5