Square of an Odd NumberDate: 11/12/2002 at 09:18:54 From: James Terris Subject: Divisibility Is this true or false? The square of any odd number can be represented in the form 8n+1, where n is a whole number. I think the answer is true, but I can't think of a formula to prove it. Date: 11/12/2002 at 10:11:50 From: Doctor Ian Subject: Re: Divisibility Hi James, This is interesting! Thanks for asking this question. Any odd number can be represented as (2k+1), where k is any integer. So the square of an odd number is (2k+1)^2 = 4k^2 + 4k + 1 Let's _assume_ that there is some n such that 4k^2 + 4k + 1 = 8n + 1 Of course, we can subtract 1 from each side to get 4k^2 + 4k = 8n And we can divide both sides by 4 to get k^2 + k = 2n k(k+1) = 2n So now what does this equation say? It says that if we multiply two consecutive numbers, we get an even number. Which is true, since one of those numbers is going to be even. Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/