Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized for You
we will pick new questions that match your level based on your Timer History
Track Your Progress
every week, we’ll send you an estimated GMAT score based on your performance
Practice Pays
we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
It appears that you are browsing the GMAT Club forum unregistered!
Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club
Registration gives you:
Tests
Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.
Applicant Stats
View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more
Books/Downloads
Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!
Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
If x is an integer, what is the value of x? 1) |x - |x2|| = 2 2) |x2 - |x|| = 2
Hi Rohit,these type of questions are extremely easy.they just seem to be intimidating but they are not . You just need to know one concept [x]= x if x is positive [x]=-x if x is negative.
Now take 1) |x - |x2|| = 2
|x2| is always positive. |x - |x2|| is negative since x^2>x
x^2-x=2.The value of X can be obtained as 2,-1. Statement alone is not sufficient
From 2) Similarly we get 2 equations x^2-x=2 and x^2+x=2 depeding upon whether X is positive or negative respectively which we dont know . Statement 2 alone is not sufficient . _________________
If x is an integer, what is the value of x? [#permalink]
02 Feb 2012, 04:44
4
This post received KUDOS
Expert's post
4
This post was BOOKMARKED
rohitgoel15 wrote:
If x is an integer, what is the value of x? 1) |x - |x2|| = 2 2) |x2 - |x|| = 2
I saw the solution and I think i cant even get close. On the test, I would prefer not to solve this question. But is there a short way to make an educated guess.
Answer is not E as given in above posts, it's C. Also note that 1 and -1 does not satisfy statement (2).
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2. First of all: \(|x^2|=x^2\) (as \(x^2\) is a non-negative value). Square both sides: \((x-x^2)^2=4\) --> factor out \(x\): \(x^2*(1-x)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-1\) (by trial and error: the product of two perfect square is 4: 1*4=4 or 4*1=4). Not sufficient.
(2) |x^2 - |x|| = 2 --> square both sides: \((x^2-|x|)^2=4\) --> factor out \(|x|\): \(x^2*(|x|-1)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-2\). Not sufficient.
(1)+(2) Intersection of the values from (1) and (2) is \(x=2\). Sufficient.
Re: If x is an integer, what is the value of x? [#permalink]
03 Feb 2012, 08:46
Bunuel wrote:
rohitgoel15 wrote:
If x is an integer, what is the value of x? 1) |x - |x2|| = 2 2) |x2 - |x|| = 2
I saw the solution and I think i cant even get close. On the test, I would prefer not to solve this question. But is there a short way to make an educated guess.
Answer is not E as given in above posts, it's C. Also note that 1 and -1 does not satisfy statement (2).
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2. First of all: \(|x^2|=x^2\) (as \(x^2\) is a non-negative value). Square both sides: \((x-x^2)^2=4\) --> factor out \(x\): \(x^2*(1-x)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-1\) (by trial and error: the product of two perfect square is 4: 1*4=4 or 4*1=4). Not sufficient.
(2) |x2 - |x|| = 2 --> square both sides: \((x^2-|x|)^2=4\) --> factor out \(|x|\): \(x^2*(|x|-1)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-2\). Not sufficient.
(1)+(2) Intersection of the values from (1) and (2) is \(x=2\). Sufficient.
Answer: C.
Hope it's clear.
Thanks for the reply Bunuel. I didnt understand the factorization part in your post. It would be great if you can simplify the parts. But is there a mistake in the below post?
amit2k9 wrote:
a. squaring both sides we get x^2 + x^4 - 2x* x^2 = 4 meaning, x^2 (x-1)^2 = 4 thus x = 2 | -1 not sufficient.
b same process and we get x = 2| -2 not sufficient.
a+b gives x = 2.
thus C it is.
Now take 1) |x - |x2|| = 2
|x2| is always positive. |x - |x2|| is negative since x^2>x
x^2-x=2.The value of X can be obtained as 2,-1. Statement alone is not sufficient
From 2) Similarly we get 2 equations x^2-x=2 and x^2+x=2 depeding upon whether X is positive or negative respectively which we dont know . Statement 2 alone is not sufficient .
Re: If x is an integer, what is the value of x? [#permalink]
03 Feb 2012, 09:16
Expert's post
rohitgoel15 wrote:
Bunuel wrote:
rohitgoel15 wrote:
If x is an integer, what is the value of x? 1) |x - |x2|| = 2 2) |x2 - |x|| = 2
I saw the solution and I think i cant even get close. On the test, I would prefer not to solve this question. But is there a short way to make an educated guess.
Answer is not E as given in above posts, it's C. Also note that 1 and -1 does not satisfy statement (2).
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2. First of all: \(|x^2|=x^2\) (as \(x^2\) is a non-negative value). Square both sides: \((x-x^2)^2=4\) --> factor out \(x\): \(x^2*(1-x)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-1\) (by trial and error: the product of two perfect square is 4: 1*4=4 or 4*1=4). Not sufficient.
(2) |x2 - |x|| = 2 --> square both sides: \((x^2-|x|)^2=4\) --> factor out \(|x|\): \(x^2*(|x|-1)^2=4\) --> as \(x\) is an integer then \(x=2\) or \(x=-2\). Not sufficient.
(1)+(2) Intersection of the values from (1) and (2) is \(x=2\). Sufficient.
Answer: C.
Hope it's clear.
Thanks for the reply Bunuel. I didnt understand the factorization part in your post. It would be great if you can simplify the parts. But is there a mistake in the below post?
amit2k9 wrote:
a. squaring both sides we get x^2 + x^4 - 2x* x^2 = 4 meaning, x^2 (x-1)^2 = 4 thus x = 2 | -1 not sufficient.
b same process and we get x = 2| -2 not sufficient.
a+b gives x = 2.
thus C it is.
Now take 1) |x - |x2|| = 2
|x2| is always positive. |x - |x2|| is negative since x^2>x
x^2-x=2.The value of X can be obtained as 2,-1. Statement alone is not sufficient
From 2) Similarly we get 2 equations x^2-x=2 and x^2+x=2 depeding upon whether X is positive or negative respectively which we dont know . Statement 2 alone is not sufficient .
First question: factoring out. \((x-x^2)^2=4\) --> \((x*(1-x))^2=4\) --> \(x^2*(1-x)^2=4\); \((x^2-|x|)^2=4\) --> now, we want to factor out \(|x|\) (notice x^2=|x|*|x| and we are factoring out one |x|) --> \((|x|*(|x|-1))^2=4\) --> \(x^2*(|x|-1)^2=4\).
Second question: other solutions. amit2k9 corrected his solution after my post so the answer there is correct. You also quote there saikarthikreddy's solution which I don't really understand as there are some parts in reasoning missing. Also it's not clear what is saikarthikreddy's answer. E? C?
Please ask if anything remains unclear in my post. _________________
Re: If x is an integer, what is the value of x? [#permalink]
18 Dec 2012, 20:04
Bunnel if you dont mind can you explain the factorizing part bit elaborately...Am totally not able to understand the second statement factorization _________________
"Giving kudos" is a decent way to say "Thanks" and motivate contributors. Please use them, it won't cost you anything
Re: If x is an integer, what is the value of x? [#permalink]
19 Dec 2012, 02:13
Expert's post
skamal7 wrote:
Bunnel if you dont mind can you explain the factorizing part bit elaborately...Am totally not able to understand the second statement factorization
(2) |x^2 - |x|| = 2 --> square both sides: \((x^2-|x|)^2=4\). Since \(x^2=|x|^2\), then we have that \((|x|^2-|x|)^2=4\). Factor out \(|x|\): \(|x|^2*(|x|-1)^2=4\) --> \(x^2*(|x|-1)^2=4\). _________________
Re: If x is an integer, what is the value of x? [#permalink]
27 Dec 2012, 18:39
Bunuel wrote:
skamal7 wrote:
Bunnel if you dont mind can you explain the factorizing part bit elaborately...Am totally not able to understand the second statement factorization
(2) |x^2 - |x|| = 2 --> square both sides: \((x^2-|x|)^2=4\). Since \(x^2=|x|^2\), then we have that \((|x|^2-|x|)^2=4\). Factor out \(|x|\): \(|x|^2*(|x|-1)^2=4\) --> \(x^2*(|x|-1)^2=4\).
Hi Bunuel,
I understood what you did, what I didnt understand is why you squared the equation before simplifying it. What I knew about Mods, my line of reasoning is similar to what Apex231 did. I was just wondering about the approach that you took, squaring and then moving forward, clearly I am missing something here.. can you please explain.
Re: If x is an integer... [#permalink]
09 Jan 2013, 09:59
Expert's post
sambam wrote:
If x is an integer, what is the value of x?
1) |x - |x^2|| = 2 2) |x^2 - |x|| = 2
A tough one indeed. This question is not at all a sub-700 level question. IMO it is atleast 730 level question.
Statement 1 yields 2 cases, among which one provides non-real numbers. The two real number values of x are 2,-1. Insufficient.
Statement 2 yields 4 cases as well, among which 2 provide non real numbers. The 2 real number solutions of x are (-2 and 1) and (2 and -1) respectively. One doesn't satisfies the statement 2 and thus is not considered. 3 values, hence insufficient.
The common value in statement 1 solution and statement 2 solution is -2. Hence x=2 . +1C _________________
Re: If x is an integer, what is the value of x? [#permalink]
07 Jul 2013, 16:08
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2
|x - |x^2|| = 2 (x^2 is ALWAYS greater than or equal to zero so we can drop the absolute value sign) |x-x^2| = 2 Two cases, positive and negative Positive: x>1 x-x^2 = 2 -x^2 + x - 2 = 0 x^2 - x + 2 = 0 (can this be factored out?)
Here, we have two possible values for x. INSUFFICIENT
(2) |x^2 - |x|| = 2
|x^2 - |x|| = 2 Two cases for x, positive and negative. x>= 0 x^2 - x = 2 x^2 - x - 2 = 0 (x-2) * (x+1) = 0 x = 2, x = -1 two values, one less than zero one greater than zero. INSUFFICIENT
x<0 x^2 - -x =2 x^2 + x - 2 = 0 (x+2) * (x-1) = 0 x=-2, x=1 two values for x but one is greater than zero and one is less than zero. INSUFFICIENT
See, I would say E in this case. Where did I go wrong?
Solving it another way...
(1) |x - |x^2|| = 2 A stated above x^2 is greater than or equal to 0 so we can drop the absolute value signs.
(x-x^2)^2 = 4 x=2, x=-1
We get two values. INSUFFICIENT
(2) |x^2 - |x|| = 2 As with #1 we can get rid of the outer absolute value signs by squaring. |x^2 - |x|| = 2 (x^2 - |x|) = 2 (x^2 - |x|)^2 = 4 (remember, x^2 = |x|^2) (|x|^2 - |x|)^2 = 4 |x|(|x| - 1)^2 = 4 x= 2, x=-2
we get two values INSUFFICIENT
1+2 we get an intersection of x=-2 SUFFICIENT
Here is my question. There are many times where I have correctly used the first method (taking the positive and negative cases to solve) to solve problems and this seems like it could be one of those problems. Why is it that with this problem, that method appears to be incorrect?
Re: If x is an integer, what is the value of x? [#permalink]
07 Jul 2013, 22:26
Expert's post
WholeLottaLove wrote:
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2
|x - |x^2|| = 2 (x^2 is ALWAYS greater than or equal to zero so we can drop the absolute value sign) |x-x^2| = 2 Two cases, positive and negative Positive: x>1 x-x^2 = 2 -x^2 + x - 2 = 0 x^2 - x + 2 = 0 (can this be factored out?)
Here, we have two possible values for x. INSUFFICIENT
(2) |x^2 - |x|| = 2
|x^2 - |x|| = 2 Two cases for x, positive and negative. x>= 0 x^2 - x = 2 x^2 - x - 2 = 0 (x-2) * (x+1) = 0 x = 2, x = -1 two values, one less than zero one greater than zero. INSUFFICIENT
x<0 x^2 - -x =2 x^2 + x - 2 = 0 (x+2) * (x-1) = 0 x=-2, x=1 two values for x but one is greater than zero and one is less than zero. INSUFFICIENT
See, I would say E in this case. Where did I go wrong?
Thanks!
This is not the best way to solve this question.
Also, notice that: x-x^2<0 for x<0 and x>1 and x-x^2>0 for 0<x<1. _________________
Re: If x is an integer, what is the value of x? [#permalink]
11 Jul 2013, 11:49
If x is an integer, what is the value of x?
(1) |x - |x^2|| = 2
|x - |x^2|| = 2 (we can drop the inner absolute value signs because x^2 is always >= 0) |x - x^2| = 2
Normally, there would be a positive and a negative case Positive: 0<x<1 Negative: x>1, x<0
However, because x must be an integer, there is no positive case to test because only a fraction between 0 and 1 will provide a positive case.
Negative: x>1, x<0 |x - x^2| = 2 -(x-x^2) = 2 -x + x^2 = 2 x^2 - x - 2 = 0 (x - 2)(x + 1) = 0 x=2, x=-1 Both values of x satisfy their given ranges (2>1 and -1<-0) So we are left with two possible correct answers INSUFFICIENT
(2) |x^2 - |x|| = 2
|x^2 - |x|| = 2 Two cases:
X is an integer so it must be greater than or equal to 1 or less than or equal to -1. This means that |x^2 - |x|| = 2 will always be positive but |x| could be positive or negative.
Re: If x is an integer, what is the value of x? [#permalink]
23 Aug 2014, 16:36
Hello from the GMAT Club BumpBot!
Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).
Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________
If x is an integer, what is the value of x? [#permalink]
10 Sep 2014, 04:45
Hey bunuel, I got x=-1,2 from the first statement. But in the second statement, i took positive and negative possibilities and came up with 4 equations. the 4 equations are 1.(x^2)-x=2 2.(x^2)+x=2 3. -(x^2)+x=2 4. -(x^2)-x=2 Out of these four equations, according to me, only the 1st and the second have real solutions. So from the 1st equation above i got x=-1,2(Same as the result from our First Statement ) and from the second equation i got x=1,-2. But everywhere people have written that they got x=-2,2 from the second statement. Can you please explain it to me as to what the issue is.
gmatclubot
If x is an integer, what is the value of x?
[#permalink]
10 Sep 2014, 04:45
The “3 golden nuggets” of MBA admission process With ten years of experience helping prospective students with MBA admissions and career progression, I will be writing this blog through...
You know what’s worse than getting a ding at one of your dreams schools . Yes its getting that horrid wait-listed email . This limbo is frustrating as hell . Somewhere...