\[\boxed{\mathbf{1333.еуроки - ответы\ на\ пятёрку}}\]
\[\mathbf{а)\ }\]
\[MA = \sqrt{4^{2} + 3^{2}} = 5\ см.\]
\[MA \cdot MB = 4 \cdot 10\]
\[MB = \frac{40}{5} = 8.\]
\[AB = MB - MA = 8 - 5 = 3\ см.\]
\[\textbf{б)}\ \]
\[MA^{2} = 3 \cdot 12 = 36\]
\[MA = 6\ см.\]
\[\textbf{в)}\ \]
\[MC = \sqrt{4^{2} + 3^{2}} = 5\ см.\]
\[MA \cdot MC = 2 \cdot 4\]
\[5 \cdot MA = 8\]
\[MA = 1,6\ см.\]