Giải các hệ phương trình :
$\begin{array}{l}
1)\,\,\,\left\{ \begin{array}{l}
{9^x}{.3^y} = 81\\
\lg {\left( {x +y } \right)^2} - \lg x = 2\lg 3
\end{array} \right.\,\,\,\,\,\,\,\,(1)\\
2)\,\,\left\{ \begin{array}{l}
{x^{\sqrt y + x}} = {y^{\frac{4}{3}}}\\
{y^{x + \sqrt y }} = {x^{\frac{4}{3}}}
\end{array} \right.\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(2)
\end{array}$