If the sum of n terms of an arithmetic progression Sn = n2 – n, then the third term of the series is ______.

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If the sum of n terms of an arithmetic progression Sn = n2 – n, then the third term of the series is 4. Explanation: For any series the nth term an = Sn – Sn – 1. Here, Sn = n2 – n. So, Sn – 1 = (n – 1)2 – (n – 1) And an = (n2 – n) – [(n – 1)2 – (n – 1)] = 2n – 2 Thus, a3 = 2 $\times$ 3 – 2 = 4.

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