Question

Комбинаторика:
$C left {{1} atop {4}} right. + C left { {{9} atop {48}} right. =???$

Answer 1

$frac{4!}{1!(4-1)!} * frac{48!}{9!(48-9)!}= frac{4!}{3!} } * frac{48!}{9!*39!} =4* frac{40*41*42*43*44*45*46*47*48}{2*3*4*5*6*7*8*9} =\=4*40*41*43*11*46*47=6708426560$