Jawab:

a. Nilai a = -4 dan b = 3

b. Nilai f(-5) = 23 dan f(7) = -25

Penjelasan dengan langkah-langkah:

» Bagian a

f(x) = ax + b

f(-2) = 11 → -2a + b = 11 … pers (1)

f(5) = -17 → 5a + b = -17 … pers (2)

Eliminasi b:

-2a + b = 11

5a + b = -17 -

-7a = 28

   a = -²⁸⁄₇

   a = -4

Substitusi a ke pers (2):

  5a + b = -17

5(4) + b = -17

  20 + b = -17

           b = -17 + 20

           b = 3

Rumus fungsi:

f(x) = ax + b

f(x) = -4x + 3

┄

» Bagian b

Nilai f(-5):

f(-5) = -4(-5) + 3

        = 20 + 3

        = 23

Nilai f(7):

f(7) = -4(7) + 3

      = -28 + 3

      = -25