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 Post subject: Challenge Problem #2Posted: Tue, 12 Aug 2003 13:18:59 UTC
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Joined: Mon, 19 May 2003 19:55:19 UTC
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Location: Lexington, MA
Find the sum of this series:

.

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 Post subject: Posted: Tue, 12 Aug 2003 14:06:19 UTC
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Joined: Sun, 4 May 2003 16:04:19 UTC
Posts: 2906
yay!

1+1*1!+2*2!+...+n*n!
notice k*k!+k=(k+1)*k!=(k+1)!

so if i add one, i get:
(n+1)!
(n+1)!-1

_________________
Has anyone noticed that the below is WRONG? Otherwise this statement would be true:

where

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 Post subject: Posted: Tue, 12 Aug 2003 16:54:01 UTC
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Joined: Mon, 19 May 2003 19:55:19 UTC
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Location: Lexington, MA
Well done, Bugz!

For those of you who didn't follow Bugz' elegant solution,
I'll post a detailed explanation in a day or so.

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 Post subject: Solution #2Posted: Tue, 12 Aug 2003 20:41:22 UTC
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Joined: Mon, 19 May 2003 19:55:19 UTC
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Location: Lexington, MA
Here's the book's solution to Challnge Problem #2.

If you're still working on it, don't look beyond the wavy line.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We have:

Add the quantity and subtract it.

. . .

Every cancels out except:

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 Post subject: Posted: Fri, 15 Aug 2003 06:06:47 UTC
 S.O.S. Oldtimer

Joined: Sun, 29 Jun 2003 18:38:23 UTC
Posts: 166
Location: Earth
This reminds me of an arml question.

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