If g(x)=3x−1g(x) = 3x - 1g(x)=3x−1 and (f∘g)(x)=9x2−6x+5(f \circ g)(x) = 9x^2 - 6x + 5(f∘g)(x)=9x2−6x+5, find f(x)f(x)f(x).
f(x) = x^2 + 4
f(x) = 3x^2 + 2
f(x) = x^2 - 4
f(x) = (x+1)^2