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   demofox (demofox@mastodon.gamedev.place)'s status on Tuesday, 01-Apr-2025 05:49:03 JST demofox

   My 10yo son said he noticed something odd about multiplication.
   If you have some number C, then (C+1)*(C-1) is 1 less than C*C.
   We started exploring and it worked with any C we tried.
   We tried +/-2 and it was 4 less. He said he thought it was going by the square.
   So we tried +/-3 and yep, it was 9 less.
   C doesn't have to be an integer either.
   It was a cool pattern he noticed and it was fun getting to explore math with him.
   He surprised me a bit with that kind of an insight.

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     demofox (demofox@mastodon.gamedev.place)'s status on Tuesday, 01-Apr-2025 05:49:12 JST demofox

     in reply to

     Now that I write it out it's more obvious. You can just FOIL :P
     (C+N)(C-N) = C^2 - N^2

     Haelwenn /элвэн/ :triskell: likes this.