diketahui fungsi f(x)= ax + b jika f (2)= -2 dan f (3) =13 tentukan nilai f (4)

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

2a +b = -2
3a + b =13
---------------  - 
      -a  =  -15
       a = 15

2a + b = -2
2(15) + b = -2
   30 + b = -2
         b = -32

f(x) = ax + b

f(2) = 2a + b = -2
f(3) = 3a + b = 13
        ------------------- (-)
                   a = 15
subtitusikan nilai a = 15 ke
2a + b = -2
2(15) + b = -2
b = -2 - 30
b = -32

f(x) = 15x - 32
f(4) = 15(4) - 32
      = 60 - 32
      = 28