V
votrantunglinh


Chứng minh rằng:<br>2nC0- 2nC1+...+ (-1)^n.2nCn= [(-1)^n.2nCn]/2 <img smilieid="44" class="inlineimg" src="http://diendan.hocmai.vn/images/smilies/42.gif" border="0"><img smilieid="44" class="inlineimg" src="http://diendan.hocmai.vn/images/smilies/42.gif" border="0"><img smilieid="44" class="inlineimg" src="http://diendan.hocmai.vn/images/smilies/42.gif" border="0"><br>