g(x) = x+1 , (fog)(x)= x kuadrat +3x+4. tentukan f(x)!

g(x) = y
x+1 = y
x = y-1

f(x) = f(y-1) = (fog)(y-1)

f(x) = (y-1)²+3(y-1)+4
f(x) = y²-2y+1+3y-3+4
f(x) = y²+y+2

f(x) = x²+x+2

karena g(x) = x + 1, maka

(fog)(x)= x² + 3x + 4 = f (g(x))

x² + 3x + 4 = f (x + 1),

misal x + 1 = y → ubah x+1 jadi y
maka x = y - 1 → ubah x jadi y - 1

x² + 3x + 4 = f (x + 1)
(y - 1)² + 3(y - 1) + 4 = f(y)
f (y) = y² - 2y + 1 + 3y - 3 + 4
f(y) = y² + y + 2

maka f(x) = x² + x + 2 ✔️

semoga jelas dan membantu