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apple_pi
 3 years ago
Sum of first n triangle numbers
apple_pi
 3 years ago
Sum of first n triangle numbers

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cwrw238
 3 years ago
Best ResponseYou've already chosen the best response.01,3,6,10.. is this the series?

apple_pi
 3 years ago
Best ResponseYou've already chosen the best response.0yeah, the one generated by n(n+1)/2

cwrw238
 3 years ago
Best ResponseYou've already chosen the best response.0right  i remember that now but i don't recall the sum formula

cwrw238
 3 years ago
Best ResponseYou've already chosen the best response.0i can only suggest googling it

UnkleRhaukus
 3 years ago
Best ResponseYou've already chosen the best response.0dw:1345110210994:dw

cwrw238
 3 years ago
Best ResponseYou've already chosen the best response.0@UnkleRhaukus  good drawing

apple_pi
 3 years ago
Best ResponseYou've already chosen the best response.0Yeah, but that's only proving what we get, not how to get there

cwrw238
 3 years ago
Best ResponseYou've already chosen the best response.0yes  i see what you mean  it seems that its a guess, which is then proved by induction

nightwill
 3 years ago
Best ResponseYou've already chosen the best response.1\[S_n=\Sigma \frac{n(n+1)}{2} = \frac{1}{2} \Sigma (n^2+n) = \frac{1}{2}(\frac{n(n+1)(2n+1)}{6}+\frac{n(n+1)}{2})\] \[ =\frac{1}{12}(n(n+1)(2n+1)+3n(n+1)) = \frac{1}{12} (n(n+1)(2n+1+3)) \] \[= \frac{1}{12}(n(n+1)(2n+4)) =\frac{2}{12}(n(n+1)(n+2)) = \frac{n(n+1)(n+2)}{6}\]

apple_pi
 3 years ago
Best ResponseYou've already chosen the best response.0How did you get the sum of n^2?
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