jsgf said: “interesting”
Thursday, January 19th, 2012
Claire said: “If you take two numbers that are two apart, and multiply them, it’s the same as if you square the number in the middle and subtract one.”
Me: “Really?”
Claire: “Yeah, like nine elevens is 99, which is one less than ten tens.”
Me: “Huh. Four sixes are 24, which is one less than five fives. Five sevens are 35. Six eights are 48. You might be onto something.”
I find paper and scribble:
n(n+2) = (n+1)^2 – 1
n^2 + 2n = n^2 + 2n + 1 – 1
Me: “How about that.”
