Question

Diketahui fungsi f (X) = ax + b.jika f(3)=1 dan f(-2)=-9.Nilai f(-5)adalah ...

a.15
b.5
c.-5
d.-15

serta tuliskan cara kerjanya....

Answer 1

Dik : F(3) = 1
        F(-2) = -9
Dit : F(-5)
Jawab : F(x) = ax + b
a.F(3) = a.3 + b = 1
F(3) = 3a + b = 1... pers 1
b.f(-2) = a.(-2) +b = -9
f(2) = -2a + b = -9 ... pers 2

Eliminasi
F(3) = 3a + b = 1
F(-2) = -2a + b = -9
_________________-
5a = 10
a = 10/5 = 2 ... pers 3

Sibtutisikan pers 1 ke pers 3
f(3) = 3a + b = 1
-> 3.2 + b = 1
6 + b = 1
b = 1-6 = -5

f(-5) = ax + b
-> 2.-5 + -5
-10 + -5 = -15
Jadi, F(-5) = -15