Question: For \(f\,\left( x,\,y \right)\quad =\quad {{x}^{\,2}}\quad +\quad 4\,x\,y\quad +\quad {{y}^{\,2}}\quad -\quad 4\,x\quad +\quad 16\,y\quad +\quad 3\), find all values of \(x\) and \(y\) such that \(\frac{\delta }{\delta x}\,f\,\left( x,\,y \right)\quad =\quad 0\) and \(\frac{\delta }{\delta y}\,f\,\left( x,\,y \right)\quad =\quad 0\) simultaneously.