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comment Proof for formula for sum of sequence $1+2+3+\ldots+n$?
Here's the only pic I could find that shows the visual proof you describe: aplcenmp.apl.jhu.edu/Classes/605202/felikson/lectures/L2/…
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comment Proof for formula for sum of sequence $1+2+3+\ldots+n$?
Holy crap! I don't speak mathematics but thx anyway.
Aug
12
comment Proof for formula for sum of sequence $1+2+3+\ldots+n$?
Yep, that's it, write one backwards. I read this post but it didn't click - I guess I needed to write it out to see it. Thx
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revised Proof for formula for sum of sequence $1+2+3+\ldots+n$?
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accepted Proof for formula for sum of sequence $1+2+3+\ldots+n$?
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revised Proof for formula for sum of sequence $1+2+3+\ldots+n$?
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12
comment Proof for formula for sum of sequence $1+2+3+\ldots+n$?
I got it! It's 2S = (1+2+...+(n-1)+n) + (n+(n-1)+...+2+1) - so you write one backwards, then match up each term. 2S = (1+n) + (2+n-1)+...+(n-1+2)+n+1, and so 2S=(n+1)+(n+1)+...+(n+1)+(n+1) etc
Aug
12
comment Proof for formula for sum of sequence $1+2+3+\ldots+n$?
Well, you lost me at "each term is n+1...". As far as I can see, if you add the two equations term by term it will be: n+n + (n-1)+(n-1) + ... + 2+2 + 1+1. How did you get (n+1) + (n+1) + ... + (n+1)?
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Aug
12
asked Proof for formula for sum of sequence $1+2+3+\ldots+n$?