Jika g(x) =x+1 dan (fog) (x) =x²+3x+1. Tentukan f(x)

jwab
fungsi

fog(x) = x² + 3x + 1
f (g(x)) = x² + 3x + 1
f(x+1) = x² + 3x + 1
f(x+1-1) =  (x -1)² + 3(x -1) + 1
f(x) = x² -2x + 1 + 3x - 3 + 1
f(x)= x² + x - 1