If the sum of p terms of an AP is q and the sum of q terms is p, then show that the sum of `p+q` terms is `- (p+q)` , Also find the sum of first `p-q` terms (where , `pgtq`).

Explanation

To solve the problem step by step, we will use the formulas for the sum of an arithmetic progression (AP) and the given conditions.

### Step 1: Write the formula for the sum of the first \( p \) terms of an AP.
The sum \( S_p \) of the first \( p \) terms of an AP is given by:
\[ S_p = \frac{p}{2} \times (2a + (p - 1)d) \]
where \( a \) is the first term and \( d \) is the common difference.
...