I'm having trouble the underlined red part of this proof (attached image) of the what looks to be the alternate series test, not sure if it's an error but it's more likely I've perhaps misunderstood something.(adsbygoogle = window.adsbygoogle || []).push({});

If [itex]y_j[/itex] is defined as the sequence of partial sums of the even terms of the sequence [itex]x_j[/itex] from j=n onwards (i.e. the positive terms), then shouldn't [itex]y_{j+1}=y_j + x_{N+2j+2}[/itex]?

How does [itex]x_{N+2j+1}[/itex] come in? Thats an odd/negative term of [itex]x_N[/itex]!

And then the result is that [itex]y_j \geq y_{j+1}[/itex], but but if [itex]y_j[/tex] is the sequence of positive partial sums, then should it not be increasing?

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# Understanding this proof involving alternating series

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