764 Пользуясь правилом многоугольника, упростите выраже- ние: а) (АВ + ВC - MC) + (MD - KD); 6) (CB+AC+BD) - (MK+KD).

a) (\(\vec{AB}\) + \(\vec{BC}\) - \(\vec{MC}\)) + (\(\vec{MD}\) - \(\vec{KD}\)) = (\(\vec{AB}\) + \(\vec{BC}\) + \(\vec{CM}\)) + (\(\vec{MD}\) + \(\vec{DK}\)) = \(\vec{AC}\) + \(\vec{CM}\) + \(\vec{MK}\) = \(\vec{AM}\) + \(\vec{MK}\) = \(\vec{AK}\)

б) (\(\vec{CB}\) + \(\vec{AC}\) + \(\vec{BD}\)) - (\(\vec{MK}\) + \(\vec{KD}\)) = (\(\vec{AB}\) + \(\vec{BD}\)) - \(\vec{MD}\) = \(\vec{AD}\) - \(\vec{MD}\) = \(\vec{AD}\) + \(\vec{DM}\) = \(\vec{AM}\)

Ответ: \(\vec{AK}\); \(\vec{AM}\)