bantuinn yaa, pakek cara:)

15. f(x) = 5x - 2
f(-2)
jawab :
f(-2) = 5(-2) - 2
f(-2) = -10 - 2 = -12
jawabannya D.

16. f(x) = 4x - 5
f(a) = 15
jawab :
f(a) = 4a - 5 = 15
f(a) = 4a = 15 : -5
f(a) = 4a = -3
a = -3 - 4 = -7
gaada jawabannya.

17. f(x) = ax + b
f(3) = 5
f(-2) = -10
jawab :
f(3) = a(3) + b = 5
f(3) = 3a + b = 5
f(-2) = a(-2) + b = -10
f(-2) = -2a + b = -10
eliminasi : cara mencari A
3a + b = 5
-2a + b = -10
------------------ --
5a = 15
a = 15 : 5
a = 3
cara mencari B
3a + b = 5
3(3) + b = 5
9 + b = 5
b = 5 - 9
b = -4

rumus =
f(x) = ax + b
f(x) = 3x - 4

nilai f(8) :
f(8) = 3(8) - 4
f(8) = 24 - 4
f(8) = 20
jawabannya B

Terimakasi, semoga membantu..