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Topic: Sqrt(15) proof by prime factors
Replies: 1   Last Post: Oct 20, 2009 1:28 AM

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Posts: 1
Registered: 10/20/09
Sqrt(15) proof by prime factors
Posted: Oct 20, 2009 12:05 AM
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Having difficulty figuring out where to start on this question. The exact question is this:

Prove by considering prime factors that sqrt(15) is irrational.

sqrt(15) = sqrt(3) + sqrt(5), correct? So then I can prove that sqrt(3) and sqrt(5) are both irrational but then how does that prove that sqrt(15) is also irrational?

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