For the functions f(x) = x − 3 and g\left(x\right)=\frac{x+7}{2} g ( x ) = x + 7 2 , find [g∘f](x). Group of answer choices \frac{x^2+4x-21}{2} x 2 + 4 x − 21 2 \frac{3x+1}{2} 3 x + 1 2 \frac{x+4}{2} x + 4 2 \frac{x+1}{2}