Binomial TheoremHard

Question

If an = , then equals

Options

A.(n - 1)an
B.nan
C. nan
D.None of these

Solution

Let b = =
    Let b = =
   
= nan -      (∵ nCr = nCn-r)
= nan - b
⇒ 2b = nan       ⇒b = nan

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