Diketahui fungsi f(x) = ax + b, jika f(2) = -2 dan f(-3) = 13 maka nilai f(4) adalah...

f(2) = -2 dan f(-3)

f(2) = 2a + b = -2
f(-3)= -3a + b = 13  _  
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          5a = -15
           a = -3

substitusi a ke 2a + b = -2
2(-3) + b = -2
b = -2 + 6 = 4

jadi f(4) = -3(4) + 4 = -12 + 4 = -8