Jawaban:

Penyelesaian :

2. Fungsi f(x) = ax + b. Jika f(-2)= -11 dan f(4) = 7, Hitunglah nilai a + 2b ...

• f(x) = ax + b
• f(-2) = -11
• f(4) = 7

Buat persamaan dari rumus f(x)

f(x) = ax + b

f(-2) = a(-2) + b = -11

-2a + b = -11 ... (i)

f(4) = a(4) + b = 7

4a + b = 7 ... (ii)

Eliminasi b dari persamaan

-2a + b = -11

4a + b = 7 -

-6a = -18

a = -18/-6

a = 3

Substitusi b ke pers (ii)

4a + b = 7

4(3) + b = 7

12 + b = 7

b = 7 - 12

b = -5

Maka nilai a + 2b

a + 2b = (3) + 2(-5)

= 3 + (-10)

= 3 - 10

= -7