The sum of (p + q) th and (p $$-$$ q)th terms of an AP is equal to

What is the fourth term of an AP of n terms whos sum is n(n + 1)?

If p times the pth term of an AP is equal to q times the qth term (p ≠ q), then what is the (p + q)th term equal to? 

Let p = ln(x), q = ln(x³) and r = ln(x⁵), where x > 1. Which of the following statements is/are correct? 

I. p, q and r are in AP.

Il. p, q and r can never be in GP.

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