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

f(2)=2a+b=-2
f(3)=3a+b=13
f(3)-f(2)=a=15
3•15+b=13
45+b=13
b=-32
f(x)=15x-32
f(4)=15•4-32
=60-32=28

Bab Fungsi
Matematika SMP Kelas VIII

f(x) = ax + b

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

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

f(x) = 15x - 32

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