\[\boxed{\mathbf{1369.еуроки - ответы\ на\ пятёрку}}\]
\[\mathbf{Дано:}\]
\[MNPQ - четырехугольник;\]
\[\overrightarrow{\text{ON}} - \overrightarrow{\text{OM}} = \overrightarrow{\text{OP}} - \overrightarrow{\text{OQ}}.\]
\[\mathbf{Найти:}\]
\[Вид\ MNPQ - ?\]
\[\mathbf{Решение.}\]
\[1)\ Найдем\ разности\ векторов:\]
\[\overrightarrow{\text{ON}} - \overrightarrow{\text{OM}} = \overrightarrow{\text{ON}} + \overrightarrow{\text{MO}} =\]
\[= \overrightarrow{\text{MO}} + \overrightarrow{\text{ON}} = \overrightarrow{\text{MN}};\]
\[\overrightarrow{\text{OP}} - \overrightarrow{\text{OQ}} = \overrightarrow{\text{OP}} + \overrightarrow{\text{QO}} =\]
\[= \overrightarrow{\text{QO}} + \overrightarrow{\text{OP}} = \overrightarrow{\text{QP}}.\]
\[2)\ \overrightarrow{\text{MN}} = \overrightarrow{\text{QP}} \Longrightarrow\]
\[\Longrightarrow MN \parallel QP\ и\ MN = QP:\]
\[\mathbf{Ответ:}MNPQ -\]
\[параллелограмм.\]