404C4−4C1303C4+4C2202C4−4C3101C4 is equal to
(401)4
(101)4
0
(201)4
The given expression is the coefficient of x4 in
4C0(1+x)404−4C1(1+x)303+4C2(1+x)202−4C3(1+x)101+4C4
= Coefficient of x4 in (1+x)101−14= Coefficient of x4 in 101C1x+101C2x2+⋯4=(101)4