If the (3r)th and (r+2)th terms in the binomial expansion of (1 + x)2n are equal, then

Question

If the (3r)th and (r+2)th terms in the binomial expansion of (1 + x)2n are equal, then (A) n = r (B) n = r + 1 (C) n = 2 r (D) n = 2 r - 1

Tardigrade Admin · Accepted Answer

Given expansion is (1+x)2 n. According to the given condition, 2 n C3 r-1 2 n Cr+1 ⇒ (2 n-3 r+1) =(r+1) ⇒ 2 n =4 r ⇒ n =2 r

Q. If the $(3 r)^{t h} an d (r + 2)^{t h}$ terms in the binomial expansion of $(1 + x)^{2 n}$ are equal, then