Diketahui g(x) = x+1 dan (f°g) (x) = x^2+3x+1. Tentukan f(x) !

(f o g) (x) = x² + 3x + 1
f(g(x)) = x² + 3x + 1
f(x + 1) = x² + 3x + 1

misal x + 1 = p maka x = p - 1

f(p) = (p - 1)² + 3(p - 1) + 1
f(p) = p² - 2p + 1 + 3p - 3 + 1
f(p) = p² + p - 1
f(x) = x² + x - 1