Diketahui fungsi f(x)=ax + b jika f(4) =8 dan f(-1)= 18 maka nilai dari f(-3) adalah...

f(x) = ax+b
f(4) = 8
f(-1) = 18

f(4) = 4a+b
8 = 4a+b

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

8 = 4a+b
18 = -a+b
_______ -
-10 = 5a
-2 = a

-a+b = 18
2+b = 18
b = 16

f(-3) = -3a+b
-3(-2)+16
6+16
22