Question 747208

{{{nCr=n!/(n-r)!r!}}}....{{{n=9}}} and {{{r=4}}}

{{{9C4=9!/(9-4)!4!}}}

{{{9C4=9!/(5!4!)}}}

{{{9C4=(9*8*7*6*5*4*3*2*1)/(5*4*3*2*1(4*3*2*1))}}}

{{{9C4=(9*cross(8)2*7*cross(6)*cross(5*4*3*2*1))/(cross(5*4*3*2*1)(cross(4)*cross(3*2)*1))}}}

{{{9C4=9*2*7}}}

{{{9C4=126}}}