Tentukan bentuk fungsi jika diketahui!

f(x) = ax + b
f(1) = 4
f(3) = 8
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f(1) = a(1) + b
      = a + b = 4 ..................(1)
f(3) = a(3) + b
      = 3a + b = 8 ................(2)

Dari (1) dan (2)
a + b = 4
3a + b = 8  - 
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2a = 4
   a = 2
Subtitusikan a = 2 kers. a + b = 4
a + b = 4
2 + b = 4
   b = 2

Jadi rumus fungsi f(x) adlah
f(x) = 2x + 2