tolong jawab nomor 18, 19

18. f(x) = 2 - 4x
f(1) = 2 - 4 = -2
f(2) = 2 - 8 = -6
f(3) = 2 - 12 = -10
f(4) = 2 - 16 = -14
Rangenya = {-14, -10, -6, -2}

19. f(x) = ax + b
f(2) = 2a + b = 5
f(4) = 4a + b = 9 -
-2a = -4
a = 2
2a + b = 5
2×2 + b = 5
b = 1