Posted by **Math_stuck** on Tuesday, February 26, 2008 at 9:49am.

Prove or disprove the following: If the integer n is divisible by 3 then n^2 is divisible by 3. Use the direct method of proof as outlined in the notes.

- direct method-Math -
**drwls**, Tuesday, February 26, 2008 at 10:21am
If n is divisible by 3, it can be written 3a, where a is an integer.

n^2 = 9 a^2, where a^2 is also an integer, is also divisible by three, since 9 = 3 x 3.

I don't have your notes so have no idea what kind of proof they expect.

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