Menentukan fungsi f(x)=ax+b, f(3)=2, f(5)=8

f(x) = ax + b
f(3) = 2
a(3) + b = 2
3a + b = 2
b = 2 - 3a ... (1)
f(5) = 8
a(5) + b = 8
5a + b = 8
b = 8 - 5a ... (2)
dari persamaan (1) dan (2), dapat diketahui bahwa:
2 - 3a = 8 - 5a
5a - 3a = 8 - 2
2a = 6
a = 6 : 2 = 3
nilai a dimasukkan ke persamaan (1), sehingga:
b = 2 - 3a = 2 - 3(3) = 2 - 9 = -7
jadi, a = 3, b = -7

f(x)=ax+b = f(3)=3a+b
2 = 3a+b
f(x)=ax+b = f(5)=5a+b
8=5a+b

2=3a+b
8=5a+b -
-6 = -2a
a= -6 : -2 = 3

2=3a+b
2=3.3 + b
2=9+b
b=2-9
b=-7

f(x) =3x-7