Fungsi f dinyatakan dengan rumus f(x) = ax + b,jika f(2) = 13 dan f(5) = 22, maka rumus fungsi f(x) adalah......

f(2) = 2a + b = 13
f(5) = 5a + b = 22
-------------------------- -
-3a = - 9
a = 3

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

f(x) = ax + b
f(x) = 3x + 7

Diketahui :
f (x) = ax + b
f (2) = 13
f (5) = 22

Ditanya : Rumus fungsi f (x) ?

Dijawab :
f (2) = 13
2a + b = 13........(pers.1)

f (5) = 22
5a + b = 22......(pers.2)

Eliminasi pers.1 dan 2
2a + b = 13.......(pers.1)
5a + b = 22.....(pers.2)
________ _
-3a = -9
a = -9 / (-3)
a = 3

Substitusikan a = 3 ke pers.1 atau 2
2a + b= 13
2 (3) + b = 13
b = 13 - 6
b = 7

Rumus fungsi f (x)
f (x) = ax + b
f (x) = 3x + 7

Jadi, rumus fungsi f (x) adalah 3x + 7