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Math Help - binomial coefficients/Pascal triangle shortcut with a negative?

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    (solved)binomial coefficients/Pascal triangle shortcut with a negative?

    I am learning how to expand binomial coefficients using Pascal's Triangle.
    All the examples I see are when 'a' and 'b' are positive. What is the trick in terms of signs when either 'a' or 'b' is negative?
    Last edited by delgeezee; September 30th 2011 at 02:42 PM.
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    Re: binomial coefficients/Pascal triangle shortcut with a negative?

    Quote Originally Posted by delgeezee View Post
    I am learning how to expand binomial coefficients using Pascal's Triangle.
    All the examples I see are when 'a' and 'b' are positive. What is the trick in terms of signs when either 'a' or 'b' is negative?
    Here is an example.
    (x-2y)^5=x^5+5x^4(-2y)+10x^3(-2y)^2+10x^2(-2y)^3+5x(-2y)^4+(-2y)^5.
    Last edited by Plato; September 30th 2011 at 02:42 PM.
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    Re: binomial coefficients/Pascal triangle shortcut with a negative?

    Quote Originally Posted by Plato View Post
    Here is an example.
    (x-2y)^5=x^5+5x^4(-2y)+10x^3(-2y)^4+10x^2(-2y)^3+5x(-2y)^4+(-2y)^5.
    Thanks, that makes sense!
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