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If a(1)gt0 for all i=1,2,…..,n. Then, th...

If `a_(1)gt0` for all `i=1,2,…..,n`. Then, the least value of
`(a_(1)+a_(2)+……+a_(n))((1)/(a_(1))+(1)/(a_(2))+…+(1)/(a_(n)))`, is

A

`n^(2)`

B

2n

C

n

D

`(1)/(n)`

Text Solution

Verified by Experts

The correct Answer is:
B

Using `A.M.geG.M.,` we have
`(a_(1)+a_(2)+...+a_(n))/(n)ge(a_(1)a_(2)...a_(n))^(1//n)" "...(i)`
`implies(a_(1)+a_(2)+...+a_(n))gen(a_(1)a_(2)...a_(n))^(1//n)`
Again, using `A.M.geG.M.,` we have
`((1)/(a_(1))+(1)/(a_(2))+...+(1)/(a_(n)))/(n)ge((1)/(a_(1))xx(1)/(a_(2))xx...xx(1)/(a_(n)))^(1//n)`
`implies((1)/(a_(1))+(1)/(a_(2))+...+(1)/(a_(n)))gen((1)/(a_(1)a_(2)......a_(n)))^(1//n)" "...(ii)`
From (i) and (ii), we get
`(a_(1)+a_(2)+...+a_(n))((1)/(a_(1))+(1)/(a_(2))+...+(1)/(a_(n)))`
`gen|a_(1)a_(2)......a_(n)|^(1//n)xx{(n)/((a_(1)a_(2)....a_(n)))}^(1//n)`
`implies(a_(1)+a_(2)+....+a_(n))((1)/(a_(1))+(1)/(a_(2))+....+(1)/(a_(n)))gen^(2)`
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