Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


Morbine
Posts:
1
Registered:
10/20/09


Sqrt(15) proof by prime factors
Posted:
Oct 20, 2009 12:05 AM


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?



