If \int {x e^{x}}/\sqrt{(1+e^{x})}} d x=f(x) \sqrt{(1+e^{x})}-2 lng(x)+c, then

g(x)= \sqrt{(1+e^{x})}-1}/\sqrt{(1+e^{x})}+1}

g(x)= \sqrt{(1+e^{x})}+1}/\sqrt{(1+e^{x})}-1}