Math CentralQuandaries & Queries


Question from Lan, a student:

Find the sum 4 + 10 + · · · + (6n − 2). The answer is 3(n^2) + n. How?

Hi Lan,

This is an arithmetic progression, the first term is 4 and subsequently each term is 6 more than the previous term. There is a technique to sum an arithmetic progression due to Gauss. Try it on your example and write back if you need more assistance.


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