If xy is greater than 0, does (x-1)(y-1)=1?
1) x+y=xy
2) x=y
Can someone explain to me why stat 2 is not sufficient? thanks!
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Frankenstein
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Hi,
We need to check: Is (x-1)(y-1)=1 =>xy-x-y+1=1 =>xy=x+y
So, in essence we ened to check: Is xy = x+y?
From(1): It is clear
sufficient
From(2)x=y
So, we need to check if x.x=x+x i.e., x^2=2x?
Not sufficient
Hence, A
We need to check: Is (x-1)(y-1)=1 =>xy-x-y+1=1 =>xy=x+y
So, in essence we ened to check: Is xy = x+y?
From(1): It is clear
sufficient
From(2)x=y
So, we need to check if x.x=x+x i.e., x^2=2x?
Not sufficient
Hence, A
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
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djiddish98
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(x-1)(y-1) = 1?
Statement 2 says x=y. However, x and y could be any number (3,20,-1/2), so we're not sure if it's 1.
Statement 2 says x=y. However, x and y could be any number (3,20,-1/2), so we're not sure if it's 1.
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Brent@GMATPrepNow
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I like how Frankenstein rewrote the target question as "Is xy = x+y?"joshua868 wrote:If xy is greater than 0, does (x-1)(y-1)=1?
1) x+y=xy
2) x=y
Can someone explain to me why stat 2 is not sufficient? thanks!
Statement 1
When we examine statement 1, it is clear that xy does, indeed, equal x+y
Statement 2
If x=y, then when we replace y with x in the target question, we get "Is x(x) = x+(x)?"
In other words, Is x^2 = 2x?
Well, x^2 could equal 2x if x=2 or x=0
But, x^2 doesn't equal 2x for all other values of x
Since we can't answer the target question with certainty, statement 2 is insufficient.
Brent Hanneson - Creator of GMATPrepNow.com
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Frankenstein
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Hi,joshua868 wrote:"So, we need to check if x.x=x+x i.e., x^2=2x?
Not sufficient "
@Frankenstein I'm still kind of lost
so if x^2=2x does that mean that x=0 or X=2
To check whether x^2=2x, we need to know the value of x.We do not know the value of x. So, we cannot surely say if that equality holds or not.
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
