Given:
[tex]\begin{gathered} g(x)=x^2+3_{} \\ (g\circ f)(x)=4x^2+3 \end{gathered}[/tex][tex](g\circ f)(x)=g(f(x)[/tex]
Let substitute one by one from the given options.
[tex]\begin{gathered} g(3x)=(3x)^2+3 \\ g(3x)=9x^2+3 \end{gathered}[/tex]
3x is not the function f.
[tex]\begin{gathered} g(4x)=(4x)^2+3 \\ g(4x)=16x^2+3 \end{gathered}[/tex]
4x is not the function f.
[tex]\begin{gathered} g(2x)=(2x)^2+3 \\ g(2x)=4x^2+3 \end{gathered}[/tex]
2x is the function f.
[tex]f(x)=2x[/tex]
Option C is the final answer.
