1.

The vaule of ` sum_(r=0)^(n-1) (""^(n)C_(r))/(""^(n)C_(r) + ""^(n)C_(r +1))` is equal toA. `(n-1)/(n+1)`B. `(n+1)/(2)`C. `(n(n+1))/(2)`D. `(n)/(2)`

Answer» Correct Answer - d
We have
` sum_(r=0)^(n-1) (""^(n)C_(r))/(""^(n)C_(r) + ""^(n)C_(r+1)) `
` sum_(r=0)^(n-1) (""^(n)C_(r))/( ""^(n+1)C_(r+1)) `
` sum_(r=0)^(n-1) (""^(n)C_(r))/( (n+1)/(r +1)""^(C_(r))) `
` sum_(r=0)^(n-1) (r+1)/(r+1)=(1)/(n+1)sum_(r=0)^(n-1) ( r+1) = (1)/(n+1) xx(n (n+1))/(n +1)= (n)/(2).` .


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