tolong kasih tau jawabannya beserta caranya! No 4 dan 5

4) f(x) = - 2x + b
f(9) = - 2(9) + b = - 7
b = - 7 + 18
b = 11

5) f(x) = ax + b
f(5) = 5a + b = - 7
f(-3) = - 3a + b = 9
---------------------------(-)
8a = - 16
a = - 2
5a + b = - 7
5(-2) + b = - 7
b = - 7 + 10
b = 3
f(x) = - 2x + 3
f(1) = - 2(1) + 3 = 1