If the binomial coefficients of three consecutive terms in the expansion of `(a+x)^n` are in the ratio 1:7 :42 , then find n .

The coefficients of three consecutive terms in the expansion of (1 + a)^n are are in the ratio 1: 7: 42 Find n.

If the coefficients of the r^(th) term and the (r + 1)^(th) term in the expansion of (1 + x)^(20) are in the ratio 1:2 , then r is equal to

The coefficients of three consecutive terms of (1+x)^(n+5) are in the ratio 5:10:14. Then n= ___________.

Find the middle terms in the expansion of (x+y)^(7) .

If the coefficient of 4th term in the expansion of (a+b)^n is 56, then n is

If the coefficients of (r-5)^th and (2r - 1)^th terms in the expansion of (1 + x)^34 are equal, find r.