g(x)=x^2+1 dan (fog)(x)=x^4-2 maka f(x)

g(x) = x² + 1
(fog)(x) = x⁴ - 2

f(x)

fog
f(g(x)) = x⁴ - 2
f(x² + 1) = x⁴ - 2
misal a = x² + 1
a - 1 = x²

f(a) = (x²)² - 2
= (a - 1)² - 2
= a² -2a + 1 - 2
= a² -2a - 1
f(x) = x² -2x -1 -----> c.