tolong jwb no 15-17.................!!!!!

15) f(1) = a + b = -4
f(-1) = -a + b = -10___+
2b = -14
b = -7

a + (-7) = -4
a = 3

a + b
= 3 + (-7)
= -4 (B)

16) f(1) = a + b = 1
f(-3) = -3a + b = -5___-
4a = 6
a = 3/2

(3/2) + b = 1
b = - 1/2

a : b
= (3/2) : (-1/2)
= -3 (C)

17) f(a) = 5a - 2 (1 + 3a) = -5
5a - 2 - 6a = -5
-a = -3
a = 3

f(3+2) = 25 - 2 (1+15)
= 25 - 2(16)
= 25 - 32 = 7 (C)