\[\begin{array}{l}
{\left( {3 - a} \right)^2} - \sqrt {0,2} .\sqrt {180{a^2}} \\
= 9 - 6a + {a^2} - \sqrt {0,2.180{a^2}} \\
= 9 - 6a + {a^2} - \sqrt {36{a^2}} \\
= 9 - 6a + {a^2} - 6\left| a \right|\\
= \left[ \begin{array}{l}
9 - 6a + {a^2} - 6a\,\,\,\,khi\,\,\,a \ge 0\\
9 - 6a + {a^2} + 6a\,\,\,\,khi\,\,\,a < 0
\end{array} \right.\\
= \left[ \begin{array}{l}
9 - 12a + {a^2}\,\,\,\,khi\,\,\,a \ge 0\\
9 + {a^2}\,\,\,\,\,\,khi\,\,\,a < 0
\end{array} \right..
\end{array}\]
