tolong dibantu dong..!

f (x) = ax + b

f (2) = 13
2a + b = 13........(pers.1)

f (-3) = -7
-3a + b = -7........ (pers.2)

Eliminasi pers.1 dan 2
2a + b = 13
-3a + b = -7
________ _
5a = 20
a = 20/5
a = 4

Substitusikan a = 4 ke pers.1 atau 2
2a + b = 13
2 (4) + b = 13
8 + b = 13
b = 13 - 8
b = 5

Rumus fungsi f (x)
= ax + b
= 4x + 5

Nilai f (-5)
= 4x + 5
= 4 (-5) + 5
= -20 + 5
= -15

Jawabannya adalah D.-15