diketahui f(x)=ax+b jika f(2)=-4 dan f(8)=20 maka f(15)=

f(x) = ax + b

f(2) = 2a + b
-4 = 2a + b .......(1)

f(8) = 8a + b
20 = 8a + b......... (2)

eliminasi (1) (2)
-4 = 2a + b
20 = 8a + b
_________-
-24 = -6a
a = -24 : -6
a = 4

substitusi a = 4 ke persamaan (1)
2a + b = -4
2(4) + b = -4
8 + b = -4
b = -4 - 8
b = -12

maka fungsinya f(x) = 4x - 12

ditanyakan f(15)
f(15) = 4(15) - 12 = 60 - 12 = 48

f (x)=ax+b
f (2)=2a+b= -4
f(8)=8a+b=20
_______ _
-6a= -24
a= 4
f (2)=2 (4)+b= -4
8+b= -4
b= -12
f (x)=4x -12
f (15)=4 (15)-12
=60-12 = 48
maaf kalo salah