1.

The sum of the series ` sum_(r=0) ^(n) "r."^(2n)C_(r), ` isA. `2^(2n -1) `B. `n . 2^(2n-1)`C. `n 2 ^(n-1)`D. `n 2^(2n - 2)`

Answer» Correct Answer - b
We have,
`sum _(r=0) ^(n) r ""^(2n)C_(r) = sum_(r=0)^(n) r (2n)/(r) ""^(2n -1) C_(r -1)`
`sum_(r=0) ^(n) r ""^(2n)C_(r) = n sum_(r=1)^(n) (""^(2n-1)C_(r-1)+""^(2n-1)C_(r-1))`
`sum_(r=0)^(n) r ""^(2n)C_(r) = n sum_(r=0)^(n) (""^(2n-1)C_(r-1)+""^(2n - 1) C_(r-1))`
`sum_(r=0)^(n) r ""^(2n)C_(r) = n sum_(r=0)^(2n-1) ""^(2n-1)C_(r)= n2^(2n -1)`


Discussion

No Comment Found

Related InterviewSolutions