by Vikram Puri

(Noida, India)

Here's a problem about the limit at infinity of a sum. There is a very similar example at the limits at infinity main article. The limit is:

Here the strategy is the same as in the example on the main article. We realize that we can write this limit as:

And that is an arithmetic sum. The formula for an arithmetic progression is:

Pluggin that into our limit we get:

And now, factoring the denominator and simplifying:

And now we use the basic technique for finding limits at infinity. We divide everything by n: