\[\boxed{\mathbf{991.ОК\ ГДЗ - домашка\ на}\ 5}\]
\[Дано:\]
\[M_{1}\left( x_{1};0 \right);\]
\[M_{2}\left( x_{2};0 \right).\]
\[Доказаь:\]
\[d = \left| x_{1} - x_{2} \right|.\]
\[Доказательство.\]
\[d = M_{1}M_{2} =\]
\[= \sqrt{\left( x_{1} - x_{2} \right)^{2} + (0 - 0)} =\]
\[= \sqrt{\left( x_{1} - x_{2} \right)^{2}} = \left| x_{1} - x_{2} \right|.\]
\[Что\ и\ требовалось\ доказать.\]