Jika f(x)=2x²+5x-7 dan g(x)=3x-12 ,maka nilai (gof) (-2) = ... a. -21 b. -27 c. -31 d. -35 e. -39

Bab Fungsi Komposisi
Matematika SMA Kelas X

(gof) (-2)

f(-2) = 2 . (-2)² + 5 . (-2) - 7
f(-2) = 8 - 10 - 7 = -9

g(-9) = 3 . (-9) - 12
g(-9) = -27 - 12 = -39

◎◎ E ◎◎

f (x) = 2x² + 5x - 7
g (x) = 3x - 12

gof (x)
= g (f (x))
= g (2x² + 5x - 7)
= 3 (2x² + 5x - 7) - 12
= 6x² + 15x - 21 - 12
= 6x² + 15x - 33

gof (-2)
= 6x² + 15x - 33
= 6 (-2)² + 15 (-2) - 33
= 6 (4) - 30 - 33
= 24 - 30 - 33
= -6 - 33
= -39