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If x=3/4 and y=2/5 what is the value of sqrt (x^2 + 6x + 9)

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CEO
Joined: 21 Jan 2007
Posts: 2734

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Location: New York City
If x=3/4 and y=2/5 what is the value of sqrt (x^2 + 6x + 9) [#permalink]

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09 Nov 2007, 09:41
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If x=3/4 and y=2/5 what is the value of sqrt (x^2 + 6x + 9) - sqrt (y^2 - 2y +1)?

87/20

63/20

47/20

15/4

14/5

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Director
Joined: 14 Feb 2005
Posts: 999

Kudos [?]: 20 [0], given: 0

Location: New York

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09 Nov 2007, 09:52
Square root is always +ve

so it should be ( x+3 ) - ( 1- y )

As y < 1, the square root value is 1-y not Y-1

Answer is X+y+2 which is 63/20

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Manager
Joined: 02 Feb 2007
Posts: 117

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09 Nov 2007, 10:53
great point Ozmba, one thing i am not sure of, is what is the reason behind 1-y instead of y-1. If y-1 =0 then y=1. therefore y is not less than 1, it must be one to make it equal.

My way gives a wrong answer which luckily is not in the answer choices, and your way gives the right answer. I am just asking you, in case i will see it during the real thing.

Thanks a lot!

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Current Student
Joined: 18 Jun 2007
Posts: 407

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Location: Atlanta, GA
Schools: Emory class of 2010

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09 Nov 2007, 12:10
When in doubt of the shortcuts, take the long way. Just plug the numbers and solve. Ozmba has done it the quickest way. If you don't understand why it needs to be (1-y) instead of (y-1), just plug numbers and you will see how it works.

Kudos [?]: 41 [0], given: 0

09 Nov 2007, 12:10
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If x=3/4 and y=2/5 what is the value of sqrt (x^2 + 6x + 9)

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