Wikipedia:Reference desk/Archives/Mathematics/2015 December 29

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December 29

Intuitive explanation of Binomial coefficients

Could anyone tell why there are only three choices available to pick one y from a set of four boxes containing x and y as given in binomials(P.2).I think it's basically four.JUSTIN JOHNS (talk) 09:14, 29 December 2015 (UTC)

I think it's just an error in the pdf. Dbfirs 10:30, 29 December 2015 (UTC)

There is no error. Page 2 talks first about the expansion of (x+y)³, then about the expansion of (x+y)⁴. It is talking about x+y)³, when it refers to "the number of ways we can pick one y from a set of 3 boxes"—not from 4 boxes. The number of ways to pick one y from a set of 4 boxes is not even mentioned on the page. --76.69.45.64 (talk) 05:27, 30 December 2015 (UTC)

Sorry! I should have read it more carefully. Dbfirs 21:16, 30 December 2015 (UTC)

You're right about four boxes but why it says "only three choices are available" in the mentioned pdf.JUSTIN JOHNS (talk) 06:27, 31 December 2015 (UTC)

In the final paragraph of the Binomial Expansion section the linked PDF says "In case of (x + y)⁴ we have four boxes. The coefficient by x³y means the number of choices to pick one y from four boxes. There are three choices to do so." As was said above, this seems to be an error in the PDF. The coefficient of x³y in the expansion of (x + y)⁴ is 4 and there are indeed 4 ways to choose one box from four. Gandalf61 (talk) 07:30, 31 December 2015 (UTC)

Okay thanks for helping me to recognize the error in pdf.JUSTIN JOHNS (talk) 08:18, 31 December 2015 (UTC)

Dang. Sorry for missing that and being misleading. --76.69.45.64 (talk) 07:18, 1 January 2016 (UTC)