Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Show that if 3 divides n^2, 3 divides n

  1. Mar 1, 2006 #1
    Show that if 3 divides n^2, 3 divides n. Hint: n can only be in the form 3a, 3a + 1, 3a + 2

    Can someone help me with this? It's pretty simple, I just don't know how to express it mathematically.
  2. jcsd
  3. Mar 1, 2006 #2


    User Avatar
    Science Advisor

    n2 then has three possibilities.
    Only the first (for n=3a) is divisible by 3. The other two have a remainder of 1 after division by 3.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook