\[\boxed{\ \mathbf{412\ (412)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ a \cdot 5 = 5\ при\ a = 1\]
\[2)\ a \cdot 5 = 0\ при\ a = 0\]
\[3)\ a \cdot 5 = a\ при\ a = 0\]
\[4)\ a \cdot 1 = 1\ при\ a = 1\]
\[5)\ a \cdot 1 = a\ при\ a = любое\ \]
\[число\]
\[6)\ a \cdot a = a\ при\ a = 0;\ \ a = 1\]
\[7)\ 0 \cdot a = a\ \ при\ a = 0\]
\[8)\ 0 \cdot a = 0\ при\ a = любое\ \]
\[число\]
\[9)\ a \cdot a = 0\ при\ a = 0.\]
\[\boxed{\mathbf{412}\mathbf{\ (375)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]