Diketahui g(x) =x+1 dan fog (x) = x²+3x+1.tentukan f(x)

f(g(x)) = x^2 + 3x + 1
f(x+1) = x^2 + 3x + 1

misal x+1 = t, maka x=t-1

f(t) = (t-1)^2 + 3(t-1) +1
= t^2 -2t + 1 + 3t - 3 + 1
= t^2 + t - 1

f(x) = x^2 + x - 1