diketahui f(x)=ax+b dan f(1) =5 , f(-2)=-1 . nilai f(4) = ...

cari nilai a dan b
f(x)=ax+b
f(1)=a(1)+b
a+b=5

f(-2)=a(-2)+b
-2a+b=-1

Eliminasi
a +b=5
-2a+b=-1
__________-
3a =6
a=6
Substitusi
a+b=5
(6)+b=5
b=(-1)

f(4)=6x+(-1)
=6(4)+(-1)
f(4)=23