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If `C_(0), C_(1), C_(2),..., C_(n)` denote the binomial coefficients in the expansion of `(1 + x)^(n)` , then . `1. C_(1) - 2 . C_(2) + 3.C_(3) - 4. C_(4) + ...+ (-1)^(n-1) nC_(n)=` |
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Answer» Correct Answer - a We have , `1. C_(1) - 2 . C_(2)+ 3. C_(3) + ...+ (-1).""^(n-1)nC_(n)` `= sum _(r=1)^(n) (-1)^(r-1) r. ""^(n)C_(r) [becausa C_(r) = ""^(n)C_(n)]` `= sum_(r=1)^(n) (-1)^(r -1)r.(n)/(r) ""^(n-1)C_(r-1)` `= sum_(r=1)^(n) (-1)^(r -1) ""^(n-1)C_(r-1)` `= n xx0 = 0 [ because sum_(r=1)^(r-1)""^(n-1)C_(r-1) = (1 -1)^(n-1) = 0]` . |
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