Jawaban:

a). f(x) = ax + b

Berdasarkan tabel, jika x = 1, maka f(x) = y = 4. Persamaannya :

f(x) = ax + b

f(1) = a(1) + b = 4

a(1) + b = 4

a + b = 4 ... pers. 1

Berdasarkan tabel, jika x = 2, maka f(x) = y = 7

Persamaannya :

f(x) = ax + b

f(2) = a(2) + b = 7

a(2) + b = 7

2a + b = 7 ... pers. 2

Eliminasi pers. 1 dan pers. 2

Eliminasi b

a + b = 4

2a + b = 7 -

-a = -3

a = 3

Substitusi a = 3 ke pers. 1.

a + b = 4

3 + b = 4

b = 4 - 3 = 1

Jadi, nilai a = 3 & nilai b = 1

b). Rumus fungsi : f(x) = ax + b

Substitusi a = 3 & b = 1 ke f(x).

f(x) = ax + b

f(x) = (3)x + (1)

f(x) = 3x + 1

Jadi, rumus fungsinya adalah f(x) = 3x + 1

c). f(x) = 3x + 1

• f(-3) = 3(-3) + 1= -9 + 1 = -8

• f(2m) = 3(2m) + 1 = 6m + 1