fungsi f(x)=ax+b,jika f(3)=13 dan f(1)=3 ,tentukan nilai -2a+b

f (x) = ax + b
f (3) = 13
f (1) = 3
3a + b = 13
1a + b = 3
________ _
2a = 10
a = 10/2
a = 5

3.5 + b = 13
15 + b = 13
b = 13 - 15
b = -2

-2a + b
= -2.5 -2
= -10-2
= -12

Maaf ya kalo salah :v