The first and last term of an A.P. are `a` and `l` respectively. If `S` is the sum of all the terms of the A.P. and the common difference is given by `(l^2-a^2)/(k-(l+a))` , then `k=` (a)`S `(b) `2S` (c) `3S` (d) none of these

Explanation

To solve the problem, we need to find the value of \( k \) given the first term \( a \), the last term \( l \), and the common difference \( D \) defined as:

\[ D = \frac{l^2 - a^2}{k - (l + a)} \]

### Step 1: Understand the sum of an A.P.

...