Diketahui g ( x ) = ax + b.
Jika g ( –2 ) = – 4 dan g ( –6 ) = 12 .
Maka bentuk fungsi g adalah ......
a. g ( x ) = –4x + 12
b. g ( x ) = –4x – 12
c. g ( x ) = –2x + 6
d. g ( x ) = –4x – 6
Jawab :
g ( x ) = ax + b
g ( –2 ) = ax + b = –4
ax + b = –4
a . –2 + b = –4
–2a + b = –4 ........... ( persamaan 1 )
g ( –6 ) = ax + b = 12
ax + b = 12
a . –6 + b = 12
–6a + b = 12 ........... ( persamaan 2 )
–2a + b = –4
–6a + b = 12 –
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–2a – ( –6a ) = –4 – 12
–2a + 6a = –16
4a = –16
a = –16 : 4
a = –4
–2a + b = –4
–2 . –4 + b = –4
8 + b = –4
b = –4 – 8
b = –12
g ( x ) = ax + b
g ( x ) = –4 . x + – 12
g ( x ) = –4x – 12
Jadi , bentuk fungsi g adalah –4x – 12 .