document.write( "Question 18148: Is there any square number besides 9 and 81 that is divisible by 9?\r
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Algebra.Com's Answer #12829 by kev82(151)\"\" \"About 
You can put this solution on YOUR website!

Yes, lots of them. This is shown below

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There is a theorem, called the fundamental theorem of arithmatic. Amongst other things it says that any whole number can be written as the product of primes. If we chose a number x, we can write it as this product of primes.

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Now consider \"3x\" and much more interestingly \"%283x%29%5E2\".

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\n" ); document.write( "\n" ); document.write( "\"3x=3%2Ap%5B1%5D%2Ap%5B2%5D%2Ap%5B3%5D%2A...\"\r
\n" ); document.write( "\n" ); document.write( "\"%283x%29%5E2=3%2A3%2Ap%5B1%5D%2Ap%5B1%5D%2Ap%5B2%5D%2Ap%5B2%5D%2Ap%5B3%5D%2Ap%5B3%5D%2A...\"
\n" ); document.write( "\"%283x%29%5E2=9%2Ap%5B1%5D%2Ap%5B1%5D%2Ap%5B2%5D%2Ap%5B2%5D%2Ap%5B3%5D%2Ap%5B3%5D%2A...\"\r
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As you can see \"%283x%29%5E2\" is a square number divisible by 9. I've just realised we didn't actually need the stuff about the primes, but it's good to learn something new everyday :D

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For your enjoyment, here are three really big square numbers divisible by 9 that I worked out

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  • 290865928967208697537677954155146591215027084823761634916418981868464451672735642563258575025

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  • 377757024764443692555739771423286715885160196068990002369

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  • 287239467617910266150742450417499640849213343093880946478917496351351184155930613119360893088100381830756

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Hope that helps

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Kev

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