diketahui f(x)= ax + b jika f(-3) =7 dan f(2)=-3, nilai f(5) adalah

Diketahui :
f(x) = ax+b
f(-3) = 7
f(2) = -3

Ditanya :
f(5) = ?

jawab :
f(x) = ax+b

f(-3) = a × (-3) + b
7 = -3a + b

f(2) = a × 2 + b
-3 = 2a + b

eliminasi :
7 = -3a + b
-3 = 2a + b
------------------ -
10 = -5a
10/-5 = -5/-5
-2 = a


subtitusi :
7 = -3a + b
7 = -3 × (-2) + b
7 = 6 + b
7-6 = b
1 = b


f(x) = ax + b
f(5) = -2 × 5 + 1
= -10 + 1
= -9