If the sum of n terms of an A.P. is `n P +1/2n(n-1)Q ,`where P and Q are constants, find the common difference.

Explanation

To solve the problem, we need to find the common difference \( d \) of the arithmetic progression (A.P.) given that the sum of the first \( n \) terms is expressed as:

\[ S_n = nP + \frac{1}{2}n(n-1)Q \]

### Step-by-step solution:

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