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furtadovinod
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Post subject: If x and y are integers such that x < y < 0, what is x – y?  Posted: Thu Jul 23, 2009 11:27 am |
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Hi,
A minor issue in the answer explanation to this problem. I am not copying out the entire explanation.
If x and y are integers such that x < y < 0, what is x – y?
(1) (x + y)(x – y) = 5
(2) xy = 6
Part of the explanation given is
As you can see, the difference between squares grows as the squares themselves get larger. The only difference between two squares that equals 5 is the difference between 4 and 9. Since x and y are both negative, this tells us that x = -3 and y = -2; therefore, x – y = -5.
The bolded portion should be
x - y = (-3) - (-2) = (-3) + 2 = -1
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www.mbachase.com
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Fri Jul 24, 2009 1:27 am |
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[Attention mbachase.com: we appreciate your desire to help GMAT students. Unfortunately, we don't host posts from competitors on our forums. If you'd like to offer free services to your students (and I think that's a great idea!), then you might consider starting your own forums. Good luck! Stacey]
Last edited by www.mbachase.com on Thu Aug 20, 2009 12:36 am, edited 1 time in total.
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Ben Ku
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Tue Aug 18, 2009 1:23 pm |
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Posts: 823
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Hi furtadovinod,
Thanks for the correction. I'll be sure to forward this to the right people so that it gets corrected on our explanations.
_________________
Ben Ku
Instructor
ManhattanGMAT
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heydharini
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Tue Oct 13, 2009 2:13 am |
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Hi,
I came across the same question in my Manhattan test today and I felt that the answer could be D
If x and y are integers such that x < y < 0, what is x – y?
(1) (x + y)(x – y) = 5
(2) xy = 6
Considering B alone here, [according to this question A is the answer and the explanation is provided - only correction needed x - y = -1]
xy = 6
The options here are -3 and -2
Since we know x<y<0 , x= -3 and y=-2
x - y = -3 - (-2) = -1
which means D should be the correct answer. Manhattan Staff, please let me know if am right?
Thanks,
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mkorrapati
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Wed Oct 21, 2009 10:57 am |
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Hey heydharini,
What about x = -6 and y = -1?
This makes xy = 6 as well.
Now you have two different solutions for x-y. So B and D can not be the answers.
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RonPurewal
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Mon Nov 02, 2009 10:23 pm |
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| ManhattanGMAT Staff |
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mkorrapati wrote: Hey heydharini,
What about x = -6 and y = -1?
This makes xy = 6 as well.
Now you have two different solutions for x-y. So B and D can not be the answers. correct.
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lancequas
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Tue May 25, 2010 11:32 pm |
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I got the answer right by accident I guess; I surmized that x^2-y^2 =5 thus x-y= +/- sq. root 5. Knowing x and y are both negative and x is farther away from zero x-y must = neg. sq. root 5. I'm still not seeing why this is wrong. Please correct me and explain the answer
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adiagr
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Sun Jun 06, 2010 3:09 pm |
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The term is [(x^2) - (y^2)] and not (x-y)^2.
You cannot take square root for the left hand side i.e. for
[(x^2) - (y^2)].
I hope that helps.
Aditya.
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RonPurewal
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Wed Jun 23, 2010 9:30 am |
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| ManhattanGMAT Staff |
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adiagr wrote: The term is [(x^2) - (y^2)] and not (x-y)^2.
You cannot take square root for the left hand side i.e. for
[(x^2) - (y^2)].
I hope that helps.
Aditya. yes. this confusion is going to be a very bad thing on the test, if it persists. therefore, you should probably pick up an algebra book -- or surf the internet -- and look up "difference of squares" and "perfect square trinomials"; these are the two factoring patterns that you are confusing. you may also want to check out the uses of the distributive property; you are mistakenly applying it to square roots, when in fact it only applies to multiplication and division.
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yousuf_azim
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Mon Sep 05, 2011 1:38 am |
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jnelson0612
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Sat Oct 15, 2011 10:40 pm |
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| ManhattanGMAT Staff |
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yousuf_azim wrote: What is the ans?
BR The answer is A.
_________________
Jamie Nelson
ManhattanGMAT Instructor
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HIK
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Fri Nov 11, 2011 9:23 am |
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Hi Guys,
Is there any way of finding out a solution algebrically?
During the exam testing numbers, always makes one wonder if there may be more solutions?
I understand that x and y are integers so the options for testing numbers is less, but still if there is an algebric solution, it'll be great.
Thanks,
Hassan
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tim
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Post subject: Re: If x and y are integers such that x < y < 0, what is x – y? Posted: Fri Nov 25, 2011 1:35 pm |
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Location: Southwest Airlines, seat 21C
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Hassan, if you are interested in a solution that uses more algebra than what you've already seen in the posts above, that is probably not a good idea. The fact that x and y are integers means that you should factor that into your solution method in order to make things easier. A purely algebraic solution that only restricts x and y to integers at the end would be much less efficient..
_________________
Tim Sanders
Manhattan GMAT Instructor
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