04-24-2014, 02:37 AM | #1 | |
Spun a twirly fruitcake,
Join Date: Feb 2009
Age: 31
Posts: 3,865
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[Math] Summation Help
So my math teacher gave me a book to work with so I can do some math work for later studies I'm aiming for. Now I've encountered something I don't understand, and luck is with me: my math teacher won't be here for the next couple of weeks >.>
Here we go! I've been given this formula to work out summations: From what I understand (just so people can see if I interpret the symbols wrong): A summation equals half of the top number (n), multiplied by (the first solution of the series (a1) + the last solution of the series (an)) With this assumption, I got this question: Which I worked out like this: But when I put the question in WolframAlpha (like most of us do I expect), it tells me the solution is 16958. I don't have pro, so I can't see a step-by-step solution. What did I do wrong? ----- Edit: I solved one summation before where this method DID work. The main difference I see is that it has k=1 instead of k=10, but it isn't explained that it makes a difference. ----- Edit minutes later: Wait, is the first formula incomplete? Because I do get 16958 if I use the length of the series (10 through 70 being 61 numbers), and not n. Is there something important that's not being told here?
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Last edited by SKG_Scintill; 04-24-2014 at 03:00 AM.. |
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