\(f´x(x,y)= -y*e^{-x-y}+2 =0\)
\(-y* e^{-x-y}+2=0|*(-1) \)
\(y* e^{-x-y}-2=0\)
\(y* e^{-(x+y)}-2=0\)
\(\frac{y}{e^{x+y}}=2\)
\(y=2*e^{x+y}=2*e^{x}*e^{y}\)
\(e^x=\frac{y}{2*e^{y}}\)
\(x*ln(e)=ln(\frac{y}{2*e^{y}})\) \(ln(e)=1\)
\(x=ln(\frac{y}{2*e^{y}})\)