This isn't homework, but I'll post it anyways because I'd like to know.(adsbygoogle = window.adsbygoogle || []).push({});

It's from Herstein's Abstract Algebra.

Show that if u = 4n + 3, where [itex]n\inN[/itex], then you can not write u in the from u = a^2 + b^2, where [itex]a,b\inN[/itex].

I feel silly for asking this, but I'm curious to know.

The one thing I do, which is obvious is that if a is odd, then b is even because u is odd. But I don't think you need this fact to solve it.

Any directions?

Please do not post solutions!!!

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