Find n if the coefficients of 4th the 13th terms in the expansion of `(a+b)^n` are equal.

If the coefficients of (p+1) th and (P+3) th terms in the expansion of (1+x)^(2n) are equal then prove that n=p+1

If the coefficients of (2r+4)th and (r-2)th terms in the expansion of (1+x)^(18) are equal.Find r?

(2) If the coefficients of (2r+4) th ,(r-2) th terms in the expansion of (1+x)^(18) are equal, find r.

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

If a:b = 3:5, and sum of the coefficients of 5^(th) and 6^(th) terms in the expansion of (a-b)^(n) is zero, then n=_________

Given positive integers r>1,n>2,n being even and the coefficient of (3r)th term and (r+2)th term in the expansion of (1+x)^(2n) are equal; find r

If the coefficients of the (2r+4)th,(r-2)th term in the expansion of (1+x)^(18) are equal, then the value of r is.

Find a if 17 th and 18 th terms in the expansion of (2+a)^(50) are equal.