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If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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01 Oct 2015, 00:49
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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01 Oct 2015, 12:31
Bunuel wrote: If x = y^2, what is the value of y – x?
(1) x = 4 (2) x + y = 2
Kudos for a correct solution. (1) x=4, y=+/2 Not Suff (2) x+y=2 > y^2+y2=0 than y=2,1 Not Suff (1+2) E
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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01 Oct 2015, 20:07
If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2 Kudos for a correct solution. st 1  x = 4 , given that x = y^2 hence y^2 = 4 , y can be 2 or 2 Hence not sufficient as we are two values of y . st 2 x + y =2 but given that x = y^2 y^2 + y = 2 y(y + 1) = 2 here also we are getting two different value of y .hence not sufficent together x=4 x+y =2 solving them we y = 2 also the value of x =4 and y = 2  satisfy x = y^2 hence ans is C
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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06 Oct 2015, 07:16
Bunuel wrote: If x = y^2, what is the value of y – x?
(1) x = 4 (2) x + y = 2
Kudos for a correct solution. VERITAS PREP OFFICIAL SOLUTION:Question Type: What Is the value? This question asks for the value of y – x. Given information from the question stem: x = y^2. While it may not be important for this question, you should train yourself to notice things like “x cannot be negative” here, as y^2 has to be > 0. Statement 1: x = 4. This is not sufficient because even taken with the fact above it still results in two answers. Substitute x in the equation from the facts and you get 4 = y^2. So y can equal 2 or – 2. These two values for y will give you different answers for “y – x” and are therefore not specific enough. You need a single value in order to be sufficient and you do not have one. The answer will either be B, C, or E. Statement 2: x + y = 2. This is not sufficient even if taken together with the information from the question stem. A quick example using Play Devil’s Advocate might be the simplest way to show that this is not sufficient. “x = 1 and y = 1”is compatible with the given information and with Statement 2. However, so is one of our examples from statement 1 “x = 4 and y = 2.” After all 4 + 2 = 2. These different values for x and y will result in different answers to “y – x = ?” This statement is also not sufficient. The answer is either C or E. Together: Taken together the statements are sufficient. Only one set of values will work with the two statements and the fact. “x = 4 and y = 2.” The correct answer is C. One important takeaway from this question: Do not assume that a variable is positive! When people answer this question incorrectly it’s usually because they only considered 2 as a value (and not 2) for y when they saw Statement 1. When a statement gives you a solution for y^2, remember that y could be either positive or negative. “Forgetting about negatives” is one of the easiest (and most common) mistakes to make on Data Sufficiency problems.
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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09 Nov 2018, 08:59
gmatbusters wrote: Project DS Butler: Day 4: Data Sufficiency (DS2) For DS butler Questions Click Here If \(x = y^2\), what is the value of \(y  x\) ? 1) \(x = 4\) 2) \(x + y = 2\)ST 1. x = 4 i.e. 4 = y^2 , but y can be 2 not sufficient ST 2 x + y = 2 i.e x = y^2 then it means x =1 ; y =1 Sufficient IMO: B hopefully I am correct



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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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Updated on: 09 Nov 2018, 09:38
gmatbusters wrote: Project DS Butler: Day 4: Data Sufficiency (DS2) For DS butler Questions Click Here If \(x = y^2\), what is the value of \(y  x\) ? 1) \(x = 4\) 2) \(x + y = 2\) tricky.
\(x =y^2\)
y  x
\(y  y^2\)
Statement 1: x = 4. \(y^2 = 4\). y = +2 or  2 .Not sufficient.
Statement 2:
x + y =2
\(y^2 + y = 2.\)
\(y^2 + y 2 = 0\)
( y + 2 ) ( y  1) = 0
y + 2 = 0
y = 2
or
y 1 = 0
y = 1.
Not sufficient.
Combining : common value is  2. Sufficient.
Originally posted by selim on 09 Nov 2018, 09:09.
Last edited by selim on 09 Nov 2018, 09:38, edited 2 times in total.



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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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09 Nov 2018, 09:25
Quote: If \(x = y^2\), what is the value of \(y  x\) ? Quote: 1) \(x = 4\) \(y^2\) = 4 Take square root on both side: y = 2 y = 2, 2 Quote: 2) \(x + y = 2\) \(y^2\) + y  2 = 0 (y+2)(y1) = 0 y = 1, 2 Combining both, y = 2.
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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09 Nov 2018, 09:34
Given: \(x = y^2\) Stmt 1: x = 4, hence \(4 = y^2\) or y = +2 or 2, which will give different values for y  x, hence insufficient. Eliminate A, D Stmt 2: x + y = 2 or y^2 + y  2 = 0 which gives: (y+2)*(y1) = 0 which gives, y = 1 or y = 2. Again, 2 values for y gives 2 values for y  x, hence insufficient. Eliminate B. Combined: if x = 4, then substitute in x + y = 2 to get, y = 2, hence y  x = 24 = 6, hence sufficient. Eliminate E Hence Option C
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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09 Nov 2018, 20:31
gmatbusters wrote: If \(x = y^2\), what is the value of \(y  x\) ? 1) \(x = 4\) 2) \(x + y = 2\) Question: \(yx = ?\)Given: \(x = y^2\)Statement 1: \(x = 4\)i.e. \(y^2 = 4\) i.e. \(y = +2\) i.e. \(yx = 24 or 24\) NOT SUFFICIENT Statement 2: \(x + y = 2\)i.e. \(y^2 + y = 2\) i.e. \(y(y1) = 2\) i.e. \(y = 2\) OR \(y = 1\) NOT SIFFICIENT Combining the two statements\(x + y = 2\) and \(x=4\) i.e. \(y = 2\) SUFFICIENT Answer: Option C
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Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2
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09 Nov 2018, 23:31
gmatbusters wrote: Project DS Butler: Day 4: Data Sufficiency (DS2) For DS butler Questions Click Here If \(x = y^2\), what is the value of \(y  x\) ? 1) \(x = 4\) 2) \(x + y = 2\)Stmnt 1: we get y=+/2 not sufficient stmtnt 2: we y(y+1)=2 y=2 and y=1 not sufficient combining two stmnts: we get y=2 , sufficient C




Re: If x = y^2, what is the value of y – x? (1) x = 4 (2) x + y = 2 &nbs
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