If f(x)=x2−2xf(x) = x^2 - 2xf(x)=x2−2x and g(x)=x+3g(x) = x + 3g(x)=x+3, which of the following is equivalent to (f∘g)(x)(f \circ g)(x)(f∘g)(x)?
x2+4x+3x^2 + 4x + 3x2+4x+3
x2+4x+9x^2 + 4x + 9x2+4x+9
x2−2x+3x^2 - 2x + 3x2−2x+3
x2+6x+9x^2 + 6x + 9x2+6x+9