Diketahui f(×)=ax+b. Jika f(4)= -3 dan f(-2)=9. Nilai f(6) adalah

f(x) = ax + b
f(4) = a.4 + b
-3 = 4a + b ••• (1)
f(-2) = a.-2 + b
9 = -2a + b ••• (2)

4a + b = -3
-2a + b = 9
---------------- -
6a = -12
a = -2

-2a + b = 9
-2 (-2) + b = 9
4 + b = 9
b = 5

Maka,
f(x) = ax + b
f(6) = -2 (6) + 5
•••• = -7

Kelas 8 Matematika
Bab Fungsi

f(x) = ax + b

f(4) = 4a + b = -3
f(-2) = -2a + b = 9
........------------------- -
6a = -12
a = -2

4a + b = -3
4 . (-2) + b = -3
b = 8 - 3
b = 5

f(x) = -2x + 5

f(6) = -2 . 6 + 5
f(6) = -12 + 5
f(6) = -7