If the second term, in the expression a13+aa-1nis 14a52, then the value of nC3nC2 is:
4
3
12
6
Explanation of correct option.
Step 1: Find the value of n
It is given that T1+1=14a52
Therefore,
nC1(13a)n-1aa-1=14a52⇒nan-113a32=14a52⇒nan-113a32=14a52⇒n×an-113+32=14a52⇒n=14
Step 2. Find the value of nC3nC2
∴nC3nC2=C314C214=14!3!14-3!14!2!14-2!=123=4
Hence, Option (A) is correct.