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# If (1+x)y=y, which of the following must be true?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 8235
GMAT 1: 760 Q51 V42
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If (1+x)y=y, which of the following must be true?  [#permalink]

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01 Jul 2016, 02:27
00:00

Difficulty:

35% (medium)

Question Stats:

63% (01:06) correct 37% (01:17) wrong based on 124 sessions

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If (1+x)y=y, which of the following must be true?
A. x=-1 or y=0
B. x=0 or y=0
C. x=1 or y=1
D. x=-1 or y=-1
E. x=0 or y=1

*An answer will be posted in 2 days.

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"Only $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Current Student Joined: 22 Jun 2016 Posts: 223 Re: If (1+x)y=y, which of the following must be true? [#permalink] ### Show Tags 01 Jul 2016, 04:15 We have (1+x)y=y. If x=0, y=y. True If y=0, (1+x)*0=0 True So, B will be the answer. -------------------------------------------------- P.S. Don't forget to give kudos Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8235 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If (1+x)y=y, which of the following must be true? [#permalink] ### Show Tags 03 Jul 2016, 17:26 From y+xy=y, we get xy=0. Hence, the correct answer is B. _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$79 for 1 month Online Course"
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Current Student
Joined: 22 Jun 2016
Posts: 223
Re: If (1+x)y=y, which of the following must be true?  [#permalink]

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03 Jul 2016, 21:21
MathRevolution wrote:
From y+xy=y, we get xy=0. Hence, the correct answer is B.

MathRevolution
By only having xy=0, we cannot say answer is B as A and E options also satisfy the condition xy=0.

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Senior Manager
Joined: 24 Nov 2015
Posts: 480
Location: United States (LA)
Re: If (1+x)y=y, which of the following must be true?  [#permalink]

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18 Sep 2016, 04:09
(1+x)y = y
y +xy = y
y + xy - y = 0
xy = 0
so x= 0 or y = 0
Intern
Joined: 06 May 2015
Posts: 22
Re: If (1+x)y=y, which of the following must be true?  [#permalink]

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18 Sep 2016, 04:36
(1+x)Y=Y

since y is variable n we don`t know its sign hence cant eliminate directly.
so lets bring bring y to left side i.e. (1+x)y-y=0
here y is common i.e. Y(1+x-1)=0
by solving inner side of the bracket we got y(x) =0 & this is only possible when either of x or y must be zero
hence B is coorect
Senior Manager
Joined: 12 Sep 2017
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If (1+x)y=y, which of the following must be true?  [#permalink]

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24 Mar 2019, 18:48
Hello MathRevolution Bunuel !

Could someone explain to me the difference between B & E?

$$(1 + x)y = y$$

$$1 + x = 1$$

$$x = 0$$

So y could be 0 or 1.

$$(1 + 0)0 = 0$$ ... true

$$(1 + 0)1 = 1$$ ... also true

Kind regards!
If (1+x)y=y, which of the following must be true?   [#permalink] 24 Mar 2019, 18:48
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