Question
Question: Given positive integers, r \> 1, n \> 2 and the coefficients of (3r)<sup>th</sup> and (r + 2)<sup>th...
Given positive integers, r > 1, n > 2 and the coefficients of (3r)th and (r + 2)th terms in the binomial expansion of (1 + x)2n are equal, then -
A
n = 2r
B
n = 3r
C
n = 2r + 1
D
None of these
Answer
n = 2r
Explanation
Solution
2nC3r –1 = 2nCr+1
Ž 3r – 1 + r + 1 = 2n
Ž 4r = 2n
Ž 2r = n