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 Soha December 19th, 2006 03:41 PM

terms

find the third term of (2x - 3y^2)^5

 roadnottaken December 19th, 2006 04:01 PM

The third term will be 5C3a^3b^2 = 10*(2x)^3*(-3y)^2 =720x^3y^2
If you don't understand why, feel free to ask, but be specific to give us the best chance of giving you useful information.

 Soha December 19th, 2006 04:43 PM

Quote:
 Originally Posted by roadnottaken The third term will be 5C3a^3b^2 = 10*(2x)^3*(-3y)^2 =720x^3y^2 If you don't understand why, feel free to ask, but be specific to give us the best chance of giving you useful information.
yeah i dont understand at all

how did you get 5c3a^3b^2 and arrive at that answer?

 roadnottaken December 19th, 2006 05:18 PM

5C3 refers to the "combination function." nCr=n!/[r!(n-r)!] where n! (pronounced "n factorial")=n(n-1)(n-2)(n-3)...*3*2*1 for all natural numbers n, and 0!=1. In (a+b)^n, the k^th term is always nCk[a^(n-k)b^k]. Note that nCr is undefined if r>n, because (-1)! makes no sense.

 Soha December 19th, 2006 05:23 PM

oh i see thank you so very much

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