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What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3
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Author:  Bunuel [ 05 Jul 2018, 23:15 ]
Post subject:  What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

What is the value of (x - 1)(y + 1) ?

(1) x + y = 4
(2) xy = 3


M36-130

Author:  Bunuel [ 16 Nov 2021, 08:26 ]
Post subject:  Re: What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

Bunuel wrote:
What is the value of (x - 1)(y + 1) ?

(1) x + y = 4
(2) xy = 3


M36-130


Official Solution:


What is the value of \((x - 1)(y + 1)\) ?

(1) \(x + y = 4\)

The above equation has infinitely many solutions for \(x\) and \(y\). Not sufficient.

(2) \(xy = 3\)

The above equation has infinitely many solutions for \(x\) and \(y\). Not sufficient.

(1)+(2) From \(x + y = 4\) we can get that \(x=1\) and \(y=3\) or \(x=3\) and \(y=1\). For the first case, \((x - 1)(y + 1)=0\) but for the second case, \((x - 1)(y + 1)=6\). Not sufficient.


Answer: E

Author:  PKN [ 05 Jul 2018, 23:36 ]
Post subject:  Re: What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

Bunuel wrote:
What is the value of (x - 1)(y + 1) ?

(1) x + y = 4
(2) xy = 3


Individually insufficient.

combining, we have two values of both x and y for which (x - 1)(y + 1) will have two values.

hence, insufficient.
Ans (E)

Author:  mygmat0101 [ 06 Jul 2018, 11:00 ]
Post subject:  Re: What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

E

individual statements are insufficient.

we'll get two values of x and y
x =1,3 y=3,1

so the binomial has 2 values

so E

Author:  Bunuel [ 24 Dec 2018, 00:38 ]
Post subject:  Re: What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

Bunuel wrote:
What is the value of (x - 1)(y + 1) ?

(1) x + y = 4
(2) xy = 3


Par of GMAT CLUB'S New Year's Quantitative Challenge Set


Author:  Archit3110 [ 24 Dec 2018, 02:09 ]
Post subject:  Re: What is the value of (x - 1)(y + 1) ? (1) x + y = 4 (2) xy = 3

Bunuel wrote:
What is the value of (x - 1)(y + 1) ?

(1) x + y = 4
(2) xy = 3



#1: x+y= 4

x,y can be (1,3) ( 2,2,) (4,0)

insufficient

#2 xy=3
3,1 , 1/3*9 ... in sufficient

on combining we get (1,3 ) as the only number which would be sufficient .. IMO C


answer is C over E so because definite values of x & y are not sure and we get two value s in (x - 1)(y + 1) on substitution of (3,1) or (1,3)

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