1.

What is the sum of first n terms of the AP, a, 3a, 5a,………….

Answer»

AP is a, 3a, 5a,…..

Here, a = a, d = 2a

Sum = Sn = n/2 [2a + (n-1)d]

= n/2[2a + 2an – 2a]

= an2



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