jika f(2)=15 dan f(7)=25 tentukan nilai a dan b

f(2) = a + b
15 = a+ b ... pers 1

f(7) = a + 6b
25 = a + 6b... pers .2

15 = a + b
25 = a + 6b  -
- 10 = -5b
     b = 2

15 = a + 2
a = 13