Question

Suatu fungsi f dirumuskan dengan f(x) =ax +b. jika f(a) = 19, f(b) = -9, dan ab = -12, nilai f(a-b)=

Answer 1

F(a) = 19
a(a) + b = 19
a² + b = 19

f(b) = - 9
a(b) + b = - 9
ab + b = - 9
- 12 + b = - 9
b = 3

substitusi:
a² + 3 = 19
a² = 16
a = 4 atau a = - 4

utk a = 4 maka:
f(x) = 4x + 3
f(4 - 3) = f(1) = 4(1) + 3 = 7

utk a = - 4 maka:
f(x) = - 4x + 3
f(a - b) = f(-7) = - 4(-7) + 3 = 31