1.

Let `S=Sigma_(n=1)^(999) (1)/((sqrt(n)+sqrt(n+1))(4sqrt(n)+4sqrtn+1))` , then S equals ___________.

Answer» Correct Answer - 9
Given `S=sum_(n=1)^(9999)1/((sqrtn+sqrn(n+1)(root4n+root(4)(n+1)))`
`=sum_(n=1)^(9999)1/((sqrtn+sqrt(n+1))(root4n+root(4)(n+1)))((root4n-root(4)(n+1))/(root4n-root(4)(n+1)))`
`=sum_(n=1)^(9999)((n+1)^(1//4)-n^(1//4))`
`=((2^(1/4)-1)+(3^(1/4)-2^(1/4))+(4^(1/4)-3^(1/4))+....+((9999+1)^(1/4)-(9999)^(1/4)))`
`=(10^(4))^(1/4)-1`
=9


Discussion

No Comment Found