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 October 13th, 2017, 05:10 AM #1 Newbie   Joined: Oct 2017 From: Norway Posts: 3 Thanks: 0 Nice date properties (equation system?) Hi there, I recently came across some cool properties when I analyzed my birth date. 21/02/1998 21·02 = 42 19·98 = 1862; √(1862) = 43.150898… 2102+1998 = 4100 This is pretty close but not quite there. So in general I wanted to find a date of the format DD/MM/YYYY which fulfills these properties: DD·MM=x YY·YY=x² DDMM+YYYY=100x I'm not the best in mathematics so I didn't find a date but couldn't disprove that one exists as well. I'm really curious if somebody can find a date where these properties are valid. Have a nice day BGH  October 13th, 2017, 06:38 AM #2 Global Moderator   Joined: Dec 2006 Posts: 21,036 Thanks: 2273 I think the "closest" dates are 18/04/5496 and 21/02/1898. October 13th, 2017, 07:06 AM #3 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Hmmm- already missed one, gonna have to wait a long time for the other! October 13th, 2017, 07:55 AM   #4
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Quote:
 Originally Posted by skipjack I think the "closest" dates are 18/04/5496 and 21/02/1898.
I have found the dates 21/03/4197 and 13/06/6495 which are extremely close:

21/03/4197
21*03 = 63
41*97 = 3977 instead of 63² = 3969
2103+4197 = 6300

13.06.6495
13*6 = 78
64*95 = 6084 instead of 18² = 6080
1306+6495 = 7801 instead of 7800

There might be no real solution though unfortunately. October 13th, 2017, 12:51 PM #5 Global Moderator   Joined: Dec 2006 Posts: 21,036 Thanks: 2273 I assume you meant "64*95 = 6080 instead of 78² = 6084". There's also 08/10/7190: 08*10 = 80 71*90 = 6390, instead of 80² = 6400 0810 + 7190 = 8000 October 14th, 2017, 09:37 AM #6 Senior Member   Joined: Sep 2016 From: USA Posts: 670 Thanks: 440 Math Focus: Dynamical systems, analytic function theory, numerics There are no solutions. If $DM = x$ and $DM + Y = 100x$ then $x + Y = 100x$ which requires $Y = 99x$. Apply to the 2nd equation yields $Y^2 = x^2 = 99^2x^2$ requiring $x = 0$. October 16th, 2017, 11:11 AM   #7
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Quote:
 Originally Posted by SDK There are no solutions. If $DM = x$ and $DM + Y = 100x$ then $x + Y = 100x$ which requires $Y = 99x$. Apply to the 2nd equation yields $Y^2 = x^2 = 99^2x^2$ requiring $x = 0$.
But in the equation DM = x, DM is meant to be D*M whereas in DM + Y, DM is the number DM itself.

f.e.
12.01.2015
DM = 12*1 = 12
DM + Y = 1201+1000 = 2201 Tags date, equation, nice, properties, system Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post victoriamath Algebra 13 August 11th, 2014 08:48 AM mwawrzyniec Economics 1 May 12th, 2013 01:07 PM 123Peter Calculus 0 February 5th, 2011 04:09 AM Xhin Number Theory 16 September 8th, 2010 05:16 AM martsch Algebra 2 June 11th, 2009 04:27 AM

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