MA(vector)=(xA-xM)i+(yA-yM)j
MB(vector)=(xB-xM)i+(yB-yM)j
MA(vector)+MB(vector)=(xA+xB-2xM)i+(yA+yB-2yM)j
MQ(vector)=MA(vector)+MB(vector)=(xA+xB-2xM)i+(yA+yB-2yM)j=(xQ-xM)i+(yQ-yM)j
xQ=xA+xB-xM ; yQ=yA+yB-yM
|MQ|=√[(xQ-xM)²+(yQ-yM)²]=√[(5+0-2*1)²+(1-1-2*2)²]=√(1²+(-4)²)=√15