Rút gọn giá trị các biểu thức: b) √120-√5(√5+2√6-√45) c) √(-11)² -3(-√5) d) √25(a-3)² +5a (a<3)

$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\ \ \ \ \sqrt{120} -\sqrt{5} .\left(\sqrt{5} +2\sqrt{6} -\sqrt{45}\right)\\
=2\sqrt{30} -\sqrt{5} .\left(\sqrt{5} +2\sqrt{6} -3\sqrt{5}\right)\\
=2\sqrt{30} -5+2\sqrt{30} +15\\
=10
\end{array}$
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\sqrt{( -11)^{2}} -3.\left( -\sqrt{5}\right)\\
=11+3\sqrt{5}
\end{array}$
$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\sqrt{25( a-3)^{2}} +5a\ ( a< 3)\\
=5|a-3|+5a\\
=5.( -a+3) +5a\\
=-5a+15+5a\\
=15
\end{array}$