diketahui f(x) = ax + b. Jika f ( -1 ) = -8 dan f (2) = 13 , nilai f (5)

Langsung aja y

f(-1) = -a + b = -8
f(2) = 2a + b = 13
_____________-
-3a = -21
a = 7

-a + b = -8
b = -8 + 7
b = -1

f(x) = ax + b
f(x) = 7x - 1

f(5) = 7(5) - 1
f(5) = 35 - 1
f(5) = 34

Semoga berguna +_+

Diketahui:
f(x) = ax + b
f(-1) = -a + b = -8
f(2) = 2a + b = 13

Ditanyakan:
f(5)

Penyelesaian:
Eliminasi untuk mencari nilai a
2a + b = 13
-a  + b = -8
-------------- -
3a        = 21
  a = 21/3
  a = 7

Substitusi a = 7 untuk mencari b
-a + b = -8
-7 + b = -8
b = -8 + 7
b = -1

Rumus fungsi
f(x) = ax + b
f(x) = 7x - 1

Cari nilai f(5)
f(x) = 7x - 1
f(5) = 7(5) - 1
f(5) = 35 - 1
f(5) = 34