If your saying...

handshakes

handshakes

handshakes

handshakes

Then the number of each handshake when someone enters is...

The total number of handshakes is simple, its just the number of handshakes from summed

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- October 29th 2009, 09:22 AM #1

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## need help w/ this question.

Hi everybody! I have no math background and I need the ans to this question, I'd really appreciate your help.

Everytime a new person enters a room all the people that are already in the room shake hands with everybody in the room. people come in one by one. if N people entered the room how many hand shakes were made?

I kinda get how the algorithm should go but I don't know how to write the answer as a function (maybe using the sum char)

please help?

- October 29th 2009, 01:38 PM #2

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- October 29th 2009, 11:25 PM #3

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- October 30th 2009, 06:58 AM #4

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Good heavens! Every one who was already in the room shakes hands with everyone else

**again**? I think that would creep me out.

arcticm, .

It's not to difficult (but tedious) to show that the sum of k degree polynomials in n is a k+1 degree polynomial.

That is, for some number, a, b, c, and d.

Taking n= 0, so d= 0.

Taking n= 1, so a+ b+ c= 2.

Taking n= 2, so 8a+ 4b+ 2c= 8.

Taking n= 3, so 27a+ 9b+ 3c= 20.

We know that d= 0 and have 3 equations to solve for a, b, and c.