pliss bantu yaa para teman yg menganggapku teman :`…… oh ya, jangan lupa pake caranya yaa ^)

jawab

15.
f(x) = a - bx
f(-1) = -5 ---> a- b(-1) = -5
a + b = - 5

f(2)= 13 --> a - b(2) = 13
a-  2b = 13

a + b = -5
a - 2b = 13 .....(-)
3b = -18
b = - 6

a + b = - 5
a - 6 = - 5
a = 1

f(x) = a - bx
f(x) = 1 -(-6)x
f(x) = 1 + 6x
f(-5) = 1 +6(-5) 
f(-5) = - 29

16. 
garis melalui titik 
(0,1)
(1,2)
persmaan garisnya
(1-0) (y-1) = (2-1)(x -0)
1(y-1) = 1(x)
y - 1   = x
y = x + 1