f(x)=ax-b jika f(-4)=-11 dan f(4)=5 tentukan nilai 3a-b

Я не знаю как ответеть

F(X)= ax-b
F(-4)--> -4a+b = -11
F(4)--> 4a+b = 5

Eliminasi
-4a+b = -11..,,(i)
4a+b = 5..,.. (ii)
----------------- -
-8a = -16
a = 2

Substitusi ke (ii)

4(2)+b = 5
8+b = 5
B = -3

3a-b ??
3(2)-(-3) = 6+3 = 9