inequality

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inequality

by mrinal2100 » Tue Sep 14, 2010 11:35 pm
|x+2|=|y+2| what is the value of x+y?
(1) xy<0
(2) x>2 y<2


(a) When both x and y are greater than - 2 ; x + 2 = y + 2 ; x = y
(b) When both x and y are less than - 2 ; - x - 2 = - y - 2 ; x = y
(c) When x is less than -2 and y is greater than -2 ; - x - 2 = y + 2 ; x + y = - 4
(d) When x is greater than -2 and y is less than -2 ; x + 2 = - y - 2 ; x + y = - 4

1)xy<0
meaninig
x<0 y>0 or x>0 y<0


taking |x+2|=|y+2|

when -2<x<0 and y>0

x+2=y+2
x=y

when x<-2 and y>0

then -x-2=y+2
y+x=-4

insuffecient

(2) x>2 y<2

when -2<y<2 and x>2


|x+2|=|y+2|

x+2=y+2
x=y

when y<-2 and x>2


|x+2|=|y+2|

x+2=-y-2
x+y=-4

insuffecient

taking both of them together

x>2 and -2<y<2

|x+2|=|y+2|

x+2=y+2
x=y

and x>2 and y<-2


|x+2|=|y+2|

x+2=-y-2
x+y=-4
as a result answer is E

ia m confused whether my approach is correct or not
Source: — Data Sufficiency |

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by Rahul@gurome » Wed Sep 15, 2010 12:17 am
Solution:
Square both sides.
You have x^2 + 4x + 4 = y^2 + 4y + 4.
Or (x+y)(x-y) + 4(x-y) = 0.
Or (x-y)(x+y+4) = 0.
Or either x - y = 0 or x+y+4 = 0.
This means either x = y or x+y = -4.
Consider first (1) alone.
It is xy<0.
So x is not equal to y.
Or x+y = -4.
Or (1) alone is sufficient.
Next consider (2) alone.
It means again that x is not equal to y.
Or x+y = -4.
So (2) alone is also sufficient.
The correct answer is (D).
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