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Which of the following equations is NOT equivalent to 10y^2=
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11 Sep 2012, 04:37
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Re: Which of the following equations is NOT equivalent to 10y^2=
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Re: Which of the following equations is NOT equivalent to 10y^2=
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11 Sep 2012, 09:07
Bunuel wrote: The Official Guide for GMAT® Review, 13th Edition  Quantitative Questions ProjectWhich of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ? (A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10 A) dividing by 3 on either side gives the same equation as given in question stem ==> 3* 10y^2=3(x^24) ==> 3* 10^y = 3(x + 2)(x  2) ==> Q B) diving by 2 on both side ==> 2* 10y^2=2 * (x2)(x+2) ==> Q C) taking 4 to right hand side and solving ==> 10y^2=x^2  4 ==> 10y^2 = (x+2)(x2) ==> Q D) multiplying both side by 2 ==> 10y^2=2x^24 ==> left hand side can't be factored to (x2)(x+2). Hence, this is NOT equivalent to equation given in Q stem. We can stop here and mark option D. E) multiply both sides by 10 ==> 10 y^2=10 *(x^24)/10 ==> 10 y^2=(x^24) ==> 10 y^2=(x+2)(x2) ** basic formula which should be known prior to solving this question =====> (A^2  B^2) = (A+B)(AB) Other method to solve this Q is by substituting the values. The best value to take for "x" is 2 as it will make right hand side of the equation ZERO.
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Re: Which of the following equations is NOT equivalent to 10y^2=
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11 Sep 2012, 09:19
Apparently (D), since after dividing by 2, we should get 5y^2=(x^24)/2
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Re: Which of the following equations is NOT equivalent to 10y^2=
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12 Sep 2012, 12:49
Which of the following equations is NOT equivalent to 10y^2=(x+2)(x2) ? (A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10 The original equation reduces to 10y^2 = x^2 4 Option 1  3 times of equation Option 2  2 times of equation Option 3  Same as original of equation Option 4  Answer (Skip this option & jump to option 5, which in turn is right. Thus using POE this will be the answer. To cross check one can solve it) Option 5  1/10 times of equation Answer D Hope it helps
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Re: Which of the following equations is NOT equivalent to 10y^2=
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10 Dec 2012, 01:14
\(10y^2=(x+2)(x2)\) expands as \(10y^2=x^24\) (A) \(30y^2=3x^212\) Divide by 3 yields \(10y^2=x^24\) Eliminate!(B) \(20y^2=(2x4)(x+2)\) expands as \(20y2=2x^28\) Divide by 2 yields \(10y^2 = x^24\) Eliminate!(C) \(10y^2+4=x^2\) Exactly the orginal. Eliminate!(D) \(5y^2=x^22\) Multiply by 2 expands as \(10y^2= 2x^24\) It's totally different! (E) \(y^2=\frac{{x^24}}{{10}}\) Multiply by 10 expands as \(10y^2=x^24\) Eliminate!Answer: D
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Re: Which of the following equations is NOT equivalent to 10y^2=
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12 Oct 2013, 09:09
Bunuel wrote: SOLUTION
Which of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ?
(A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10
When \(x=2\), then \(10y^2=(2+2)(22)=0\) > \(y=0\).
Now, plug \(x=2\) into the answer choices and look for the option which does not give \(y=0\). Only option D gives the value of \(y\) different from zero.
Answer: D. Bunuel could we also use 2?? Thanks, C



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Re: Which of the following equations is NOT equivalent to 10y^2=
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12 Oct 2013, 09:33



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Re: Which of the following equations is NOT equivalent to 10y^2=
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27 Oct 2014, 00:48
One good thing of this question is that \(y^2\) term is on LHS of the question as well as all 5 options given. \(10y^2 = (x+2)(x2)\) For y = 0, x = 2 (Ignore ve sign aspect) Placing value of y = 0 in the OA A: \(3x^2  12 = 0; x = 2\) B: (2x4)(x+2) = 0; x = 2 C: \(x^2 = 4; x = 2\) D:\(x^2  2 = 0; x = \sqrt{2}\) >> Does not stand >> This is the answerE: Same as option C Answer = D
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Re: Which of the following equations is NOT equivalent to 10y^2=
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07 Sep 2015, 16:57
Bunuel wrote: SOLUTION
Which of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ?
(A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10
When \(x=2\), then \(10y^2=(2+2)(22)=0\) > \(y=0\).
Now, plug \(x=2\) into the answer choices and look for the option which does not give \(y=0\). Only option D gives the value of \(y\) different from zero.
Answer: D. How do you actually solve using smart numbers? When I did it, all of my answers were y=0, x=2. Let's pick x=2, when this is plugged into the equation we get y=0. So we're going to plug in 2 for all x's that we see, when y = 0 that is our answer. a. 30y^2=3x^212 3(2)^212 = 0, therefore y=0 when x=2 b. 20y^2=(2x4)(x+2) (2(2)4)(2+2) = 0, therefore y=0 when x=2 What am I doing wrong?



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Re: Which of the following equations is NOT equivalent to 10y^2=
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Updated on: 07 Sep 2015, 19:09
aces021 wrote: Bunuel wrote: SOLUTION
Which of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ?
(A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10
When \(x=2\), then \(10y^2=(2+2)(22)=0\) > \(y=0\).
Now, plug \(x=2\) into the answer choices and look for the option which does not give \(y=0\). Only option D gives the value of \(y\) different from zero.
Answer: D. How do you actually solve using smart numbers? When I did it, all of my answers were y=0, x=2. Let's pick x=2, when this is plugged into the equation we get y=0. So we're going to plug in 2 for all x's that we see, when y = 0 that is our answer. a. 30y^2=3x^212 3(2)^212 = 0, therefore y=0 when x=2 b. 20y^2=(2x4)(x+2) (2(2)4)(2+2) = 0, therefore y=0 when x=2 What am I doing wrong? I think you are missing out on what the question is asking. It is asking to find the expression that will NOT give you the same value as \(10y^2=(x+2)(x2)\) When you do use, x=2, you get the following values of 'y' A) 0 B) 0 C) 0 D) 2/5 E) 0 From the original expression you see that when you get y=0 for x=2 for options AC and E. Thus, with your 'smart numbers', D is the only expression that DOES NOT give you the same values on the left hand side as those on the right hand side. D is thus the correct answer. FYI, using smart numbers is not the best strategy for this question. You need to realize that \((A+B)(AB) = A^2B^2\) and thus the original expression becomes \(10y^2 = x^24\) D will not give you this expression and is thus the correct answer.
Originally posted by ENGRTOMBA2018 on 07 Sep 2015, 17:16.
Last edited by ENGRTOMBA2018 on 07 Sep 2015, 19:09, edited 2 times in total.
Edited the typos, alternate reasoning



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Re: Which of the following equations is NOT equivalent to 10y^2=
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07 Sep 2015, 19:05
Engr2012 wrote: aces021 wrote: Bunuel wrote: SOLUTION
Which of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ?
(A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10
When \(x=2\), then \(10y^2=(2+2)(22)=0\) > \(y=0\).
Now, plug \(x=2\) into the answer choices and look for the option which does not give \(y=0\). Only option D gives the value of \(y\) different from zero.
Answer: D. How do you actually solve using smart numbers? When I did it, all of my answers were y=0, x=2. Let's pick x=2, when this is plugged into the equation we get y=0. So we're going to plug in 2 for all x's that we see, when y = 0 that is our answer. a. 30y^2=3x^212 3(2)^212 = 0, therefore y=0 when x=2 b. 20y^2=(2x4)(x+2) (2(2)4)(2+2) = 0, therefore y=0 when x=2 What am I doing wrong? I think you are missing out on what the question is asking. It is asking to find the expression that will NOT give you the same value as \(10y^2=(x+2)(x2)\) When you do use, y = 0 and x=2, you get the following A) 15 = 15 B) 10 = 10 C) 9=9 D) 2.5 \(\neq\) 7E) 0.5 = 0.5 From the original expression you see that when you use y=0 and x=2, you get 0=0 (LHS=RHS). Thus, with your 'smart numbers', D is the only expression that DOES NOT give you the same values on the left hand side as those on the right hand side. D is thus the correct answer. FYI, using smart numbers is not the best strategy for this question. You need to realize that \((A+B)(AB) = A^2B^2\) and thus the original expression becomes \(10y^2 = x^24\) D will not give you this expression and is thus the correct answer. Thanks for the response, how are you actually getting for a. 15=15 using x=2, y=0? 30y^2=3x^212 30(0)^2 = 3(2)^2  12 What is the order of operations? Does the above equal to 0 = 0 Or does it equal to 30*1 = 3612 30 = 24 ? Either way I'm not getting 15=15. Thanks!



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Re: Which of the following equations is NOT equivalent to 10y^2=
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07 Sep 2015, 19:12
aces021 wrote:
Thanks for the response, how are you actually getting for a. 15=15 using x=2, y=0?
30y^2=3x^212 30(0)^2 = 3(2)^2  12
What is the order of operations? Does the above equal to 0 = 0
Or does it equal to 30*1 = 3612 30 = 24 ?
Either way I'm not getting 15=15. Thanks! Sorry. I had solved this using some other set of values and wrote those values. I have updated the solution. Yes, you are correct that option A will give you y=0 for x=2. As a matter of fact, options AC and E give y=0 when you use x=2. Option D does not and is thus the correct answer.



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Re: Which of the following equations is NOT equivalent to 10y^2=
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10 May 2016, 18:11
Attached is a visual that should help.
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Screen Shot 20160510 at 5.50.11 PM.png [ 76.13 KiB  Viewed 14934 times ]
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Re: Which of the following equations is NOT equivalent to 10y^2=
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25 May 2016, 09:39
Bunuel wrote: Which of the following equations is NOT equivalent to \(10y^2=(x+2)(x2)\) ?
(A) 30y^2=3x^212 (B) 20y^2=(2x4)(x+2) (C) 10y^2+4=x^2 (D) 5y^2=x^22 (E) y^2=(x^24)/10 To solve this question, we start by FOILing the right hand side of the given equation. 10y^2 = (x+2)(x2) 10y^2 = x^2 – 4 We will manipulate each of the answer choices to see if it equals 10y^2 = x^2 – 4. Let’s start with A. A) 30y^2 =3x^2 – 12If we divide this entire equation by 3 we are left with: 10y^2 = x^2 – 4 Answer choice A is not correct. B) 20y^2 = (2x4)(x+2)FOILing (2x4)(x+2) we get: 20y^2 = 2x^2 – 8 If we divide this entire equation by 2 we obtain: 10y^2 = x^2 – 4 Answer choice B is not correct. C) 10y^2 + 4 = x^2If we subtract 4 from the both sides of the equation, we obtain: 10y^2 = x^2 – 4 Answer choice C is not correct. D) 5y^2 = x^2 – 2We should notice that no matter how we try to manipulate 5y^2 = x^2 – 2, it will never be equal to 10y^2 = x^2 – 4. For example, if we multiply both sides of 5y^2 = x^2 – 2 by 2, we will have 10y^2 = 2x^2 – 4. However, that is not the same as 10y^2 = x^2 – 4. Answer D is correct. To be certain, we should also test answer E. E) y^2 = (x^2 – 4)/10If we multiply the entire equation by 10 we obtain: 10y^2 = x^2 – 4 Answer choice E is not correct. The answer is D.
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