(Fog)(x)= 4x²+8x-3 dan g(x)=2x+4. Tentukan nilai dari f(3)

Kelas 10 Matematika
Bab Fungsi Komposisi

(fog) (x) = 4x² + 8x - 3
f(2x + 4) = 4x² + 8x - 3
f(2 . x/2 + 4) = 4 . (x/2)² + 8 . x/2 - 3
f(x + 4) = 4 . x²/4 + 4x - 3
f(x - 4 + 4) = (x - 4)² + 4 (x - 4) - 3
f(x) = x² - 8x + 16 + 4x - 16 - 3
f(x) = x² - 4x - 3
f(3) = 3² - 4 . 3 - 3
f(3) = 9 - 12 - 3
f(3) = -6

Atau

f(2x + 4) = 4x² + 8x - 3

2x + 4 = 3
2x = 3 - 4
x = -1/2

4x² + 8x - 3
= 4 . (-1/2)² + 8 . (-1/2) - 3
= 4 . 1/4 - 4 - 3
= 1 - 4 - 3
= -6