F(x) =2ax + b, jika f(3) =15 dan f(1) =-1, maka f(5) =

Bab Fungsi
Matematika SMP Kelas VIII

f(x) = 2ax + b

f (3) = 2a . 3 + b = 15
               6a + b = 15

f (1) = 2a . 1 + b = -1
               2a + b = -1

6a + b = 15
2a + b = -1
----------------- -
       4a = 16
         a = 4

6a + b = 15
6 . 4 + b = 15
b = 15 - 24
b = -9

f (x) = 2a . x + b
f (x) = 2 . 4 . x + (-9)
f (x) = 8x - 9

f (5) = 8 . 5 - 9
       = 40 - 9
       = 31