Jika f(x)=ax+b f(1)=2 dan f(2)=1. Tentukan bentuk fungsi f(x)!

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

a + b = 2
-1 + b = 2
       b = 2 + 1
       b = 3

f(x) = ax + b
f(x) = -1x + 3
f(x) = -x + 3