\[\boxed{\text{173\ (173).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ \sqrt{a^{2}} = a\]
\[при\ a \geq 0;\]
\[\textbf{б)}\ \sqrt[4]{a^{4}} = - a\]
\[при\ \ a \leq 0;\]
\[\textbf{в)}\ \sqrt[3]{a^{3}} = a\]
\[a - любое.\]