The points (−2,−1),(1,0),(4,3), and (1,2) are the vertices
Toidentify−whetherABCDisa(i)parallelogram,(ii)rectangle,(iii)square,(iv)scaleneone.Solution−(i)Weknowthatinaparallelogrmthediagonalsbisecteachotheri.ethemidpointsofAC&BDaresame.LetthemidpointofACbeP(x,y).Applyingmidpointtheorem,P(x,y)=(x1+x32,y1+y32)=(−2+42,−1+32)=(1,1).AgainletthemidpointofBDbeQ(p,q).Applyingmidpointtheorem,Q(p,q)=(x2+x42,y2+y42)=(1+12,0+12)=(1,1).∴P(x,y)=Q(p,q)⟹themidpointsofAC&BDaresame.SoABCDisaparallelogram.(ii)IfthediagonalsoftheparallelogramABCDareequalthenitisarectangle.i.eAC=BD.Applyingdistanceformula,AC=√(x1−x3)2+(y1−y3)2=√(−2−4)2+(−1−3)2units=2√13units.BD=√(x2−x4)2+(y2−y4)2=√(1−1)2+(0−2)2units=2units.∴AC≠BD.SoABCDisnotarectagle.Consequently,itisnotasquare.Ans−OptionA.