If in the expansion of `(1+x)^(15),` the coefficients of `(2r+3)^(th) a n d\ (r-1)^(th)` terms are equal, then the value of `r` is a. 5 b. 6 c. 4 d. 3

Explanation

To solve the problem, we need to find the value of \( r \) such that the coefficients of the \( (2r+3)^{th} \) term and the \( (r-1)^{th} \) term in the expansion of \( (1+x)^{15} \) are equal.

### Step-by-Step Solution:

1. **Identify the General Term**:
The general term \( T_k \) in the expansion of \( (1+x)^{15} \) is given by:
\[
T_k = \binom{15}{k} x^k
...