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What is the value of X+Y?

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What is the value of X+Y?

by kguo » Sat Sep 05, 2009 8:48 am
What is the value of X+Y?

(1) X = Y - 3

(2) (2x + 3)^2 = 36

I'm just wondering why you can't square root the left and right side of statement 2 to get 2x + 3 = 6.


OA E
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Source: — Data Sufficiency |
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Re: What is the value of X+Y?

by iamaneophyte » Sat Sep 05, 2009 10:36 am
kguo wrote:What is the value of X+Y?

(1) X = Y - 3

(2) (2x + 3)^2 = 36

I'm just wondering why you can't square root the left and right side of statement 2 to get 2x + 3 = 6.


OA E
Clearly X+Y value can't be decided from the 1st option

From second option 2x+3 = +6 or -6 , so your answer will have 2 values for x and your solution can't be unique.

So option E. Hope it helps
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by kguo » Sat Sep 05, 2009 4:35 pm
so if you square root something?? you get and positive and a negative answer??

so (2x+3)^2 = 36 is equal to both

2x+3 = 6 and 2x+3 = -6?? and not just ONLY 2x+3 = 6?
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by enniguy » Sat Sep 05, 2009 8:27 pm
kguo wrote:so if you square root something?? you get and positive and a negative answer??

so (2x+3)^2 = 36 is equal to both

2x+3 = 6 and 2x+3 = -6?? and not just ONLY 2x+3 = 6?
No. It means both.
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