Let f(x)=2x\displaystyle {f{{\left({x}\right)}}}={2}\sqrt{{{x}}}

If g(x)\displaystyle {g{{\left({x}\right)}}} is the graph of f(x)\displaystyle {f{{\left({x}\right)}}} shifted down 4 units and reflected across the y-axis, write a formula for g(x)\displaystyle {g{{\left({x}\right)}}}