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/sci/ - Science & Math


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File: 82 KB, 370x405, 370px-Combinations_with_repetition;_5_multichoose_3.svg[1].png [View same] [iqdb] [saucenao] [google]
8774652 No.8774652 [Reply] [Original]

Hi! Are you good with combinatory?
We have 5 elements that cant be repeated:
1, 2, 3, 4 and 5
We need to know the combinations of this elements but there are 2 sets and the sets cant be repeated neither with other set with same elements. One sets has n elements and the other the rest of elements.
For example, with n = 2:
Set A | Set B
1 2 | 3 4 5 <- VALID

1 3 | 2 4 5 <- VALID
1 3 | 4 2 5 <- INVALID (same combination)
3 1 | 5 2 4 <- INVALID (same combination)

So there is a dependency between A and B and the "inside" elements of A and B.
Is this even possible to resolve with Maths?

>> No.8774962

I'm not sure i understand what you are saying but it seems to me that you just want to use the binomial coefficient, so in your case 5!/(n!(5-n)!)

>> No.8775072

>>8774652
I don't think I understood what you wrote. It seems like your english needs some work. But If your picture corresponds to what you're asking, then it looks kind of like the summation of consecutive triangle numbers. thus:
n(n+1)(n+2)/6