Question Number 35037 by abdo mathsup 649 cc last updated on 14/May/18
$${prove}\:{that}\:\forall\:{n}\in{N} \\ $$$$\sum_{{k}=\mathrm{0}} ^{\mathrm{2}{n}} \:\left(−\mathrm{1}\right)^{{k}} \left(\:{C}_{\mathrm{2}{n}} ^{{k}} \right)^{\mathrm{2}} \:=\left(−\mathrm{1}\right)^{{n}} \:{C}_{\mathrm{2}{n}} ^{{n}} \:\:. \\ $$