If the rth term in the expansion of `(1+x)^20` has its coefficient equal to that of the (r+ 4)th term, find r

If the coefficient of (r +1)^(th) term in the expansion of (1 +x)^(2n) be equal to that of (r + 3)^(th) term , then

(r+1)^(th) term in the expansion of (1-x)^(-4) will be

If the coefficient of (p+1) th term in the expansion of (1+x)^(^^)(2n) be equal to that of the (p+3) th term,show that p=n-1

If the coefficient of p^(th) term in the expansion of (1+x)^(n) is p and the coefficient of (p+1)^(th) term is q then n=

Show that the coefficient of middle term in the expansion of (1 + x)^(20) is equal to the sum of the coefficients of two middle terms in the expansion of (1 + x)^(19) .

In the expansion of (1+x)^(43) ,the co-efficients of (2r+1)th and (r+2)th terms are equal. Find r.