fungsi f dinyatakan dengan rumus f (x) = ax + b . jika f(-6)=32 dan f (4) = -18 , maka rumus fungsi tersebut adalah...

Diketahui
f ( x ) = ax + b
f ( - 6 ) = 32
f ( 4 ) =  -18

Penyelesaian

f ( - 6 ) = a ( - 6 ) + b
      32 = - 6a + b ( i )

f ( 4 ) = a ( 4 ) + b
  - 18 = 4a + b ( ii )

Eliminasi b

- 6a + b = 32
  4a + b = - 18
___________--
- 10a = 50
  10a = - 50
      a = - 50 ÷ 10
      a = - 5

Substitusi a = - 5

        4a + b = - 18
4 ( - 5 ) + b = - 18
      - 20 + b = - 18
                 b = - 18 + 20
                 b = 2

Rumus Fungsi = f (x) = ax + b
                             f (x) = - 5x + 2