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

1.	What is the sum of first n terms of the AP a,3a,5a...
Answer» Add Sn = n/2(2a+(n-1)dSn=n/2(2a+(n-1)2aSn=n/2(2a+2an-2a)Sn=n/2×2anSn=an²

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