1.

If `|z-4/z|=2`, then the maximum value of`|Z|`is equal to(1) `sqrt(3)+""1`(2) `sqrt(5)+""1`(3) 2(4) `2""+sqrt(2)`A. `1+sqrt(3)`B. `1+sqrt(5)`C. `1-sqrt(5)`D. `sqrt(5)-1`

Answer» Correct Answer - B
`|z-(4)/(z)|=2`
We know `|a-b|ge|a|-|b|`
` therefore |z-(4)/(z)|ge|z|-|(4)/(z)|`
`rArr 2 ge |z|-(4)/(|z|)rArr|z|^(2)-2|z|-4 le 0`
`rArr |z|=(2+-sqrt(4-4(1)(-4)))/(2(1))=(2+-sqrt(20))/(2)=(2+-2sqrt(5))/(2)=1+-sqrt(5)`
So, `z = 1 + sqrt(5)`.


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