Tolong donk soal yg nomer 5 ( yg terakhir) pd foto ini

I. g(2)=1
2a+ b = 1..........(1)
g(4) =7
4a+b = 7.........(2)
(1) dan (2)
2a + b=1. x. 2
4a+b = 7. x. 1
4a + 2b = 2
4a +b = 7. (-)
b = -5
2a + b = 1
2a + ( -5) = 1
2a = 6
a = 3

II. g (x) =3x -5

III . Soalnya gak keliatan...