$$\left. \begin{array} { l } { x ^ { 2 } y ^ { 3 } = 108 } \\ { x + y ? } \end{array} \right.$$
$x=-\frac{6\sqrt{3}}{y^{\frac{3}{2}}}\text{, }y>0\text{, }z=y-\frac{6\sqrt{3}}{y^{\frac{3}{2}}}$
$x=\frac{6\sqrt{3}}{y^{\frac{3}{2}}}\text{, }y>0\text{, }z=y+\frac{6\sqrt{3}}{y^{\frac{3}{2}}}$
