The coefficient of x5 in the expression of (1+x)21+(1+x)22+……+(1+x)30 is
The coefficient of x7 in (ax2-1/bx)11 is equal to the coefficient of x-7 in (ax-1/bx2) then ab=
The number of non zero terms in the expansion of (8+2)101 - (8-2)101 is
The coefficients of three consecutive terms in the expansion of (1+x)n are in the ratio 1:7:42, then n=
Which term of (2x-3y)12 when x=1, y=5/2 numerically greatest?