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




Re: Sqrt(15) proof by prime factors
Posted:
Oct 20, 2009 1:28 AM


Rethink your original claim...For example, we know that sqrt(2) is irrational, and by your claim, sqrt(2) = sqrt(1)+sqrt(1). But sqrt(1) = 1, making sqrt(1) rational, which would imply that sqrt(2) is rational as well. So, as a start, review (i.e. reflect on) the properties of taking square roots. Once you have that correct, you can plan a solution path...
 Original Message  From: "Morbine" <discussions@mathforum.org> To: <discretemath@mathforum.org> Sent: Monday, October 19, 2009 9:05 PM Subject: Sqrt(15) proof by prime factors
> 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? > >



