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How to prove this combinatorial summation?

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I expanded $C(m, i)$ and $C(n-1, n-i)$ and clubbed them together but it didn't yield anything useful. Please show me the approach only.

Is this the Chu-Vandermonde identity?

  • 0
    I don't understand your notation.2012-07-17
  • 0
    Yes, it is the Chu-Vandermonde identity.2012-10-29

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