suatu fungsi dirumuskan f(x)=ax+b.jika f(-2)=13 dan f(3)=-7,maka nilai f(3) adalah?...dengan cara lengkap

Jawab :

f(x) = ax + b
f(-2) = a(-2) + b = -2a + b = 13
f(3) = a(3) + b = 3a + b = -7

-2a + b = 13
3a + b = -7
____________ -
-5a = 20
a = -4

3a + b = -7
3(-4) + b = -7
-12 + b = -7
b = -7 + 12
b = 5

f(x) = ax + b = -4x + 5

Nilai f(3) = -4(-3) + 5 = 12 + 5 = 17 (C)