If xy 0, does xy y = 3? (1) xy = 3 (2) y 1 = 0

Question

If xy > 0, does xy – y = 3?
 
(1) xy = 3
(2) y – 1 = 0

Bunuel · Answer

If xy > 0, does xy – y = 3? 
 
(1) xy = 3 --> question becomes: is  3-y=3 ? or is  y=0 ? Since given that  xy>0  (or the same  xy=3 ) then it's clear that  y
eq{0}  so we have the answer NO. Sufficient.

(2) y – 1 = 0 --> question becomes: is  x=4 ? We don't know that. Not sufficient.

Answer: A.

rxs0005 · Answer

thanks great explanation

jullysabat · Answer

Good Explanation....

gmatpapa · Answer

Great! With your explanations, I am getting better at seeing through the equations and manipulating them! Thanks Kudos!

vs129 · Answer

From (1), xy-y = 3-y ; this is equal to 3 only if y=0 , but since its given that xy =3 neither x nor y can be 0. Therefore, given (1) xy-y is not equal to 3. Sufficient.
(2) simplifies the question to is x-1=3 or is x=4 which cannot be answered with this information. Insufficient.

WoundedTiger · Answer

From the given statement xy>0, we can deduce that either x,y>0 or x,y< 0 St1 we have xy=3 possible values of x and y are x=-1, y=-3, substituting in the given we get 3-(-3)=6 which is not equal to 3 x=3,y=1, we get 3-1= 2 not equal 3 x=9,y=1/3 3- 1/3= 8/3 not equal to 3 we can safely that say that for any values satisfying given st1 we do not have the expression value equal 3 Hence Option B,C,E ruled out St 2, y-1=0-----> y=1 we know only the value of y and that x>0 which is not sufficient. In order to satisfy the given equation that is xy-y=3 value of x should be 4 which we are not sure of. Hence Ans should be A

thanks

Nikkb · Answer

If xy > 0 => Either x and y both +ve or both -ve. Also both x and y not equal to 0 
Question : is xy – y = 3?

(1) xy = 3
=> if xy – y = 3 true => 3-y=3 => y=0 
As by question stem we know x and y both r non zero numbers. So above statement cant be true
Sufficient

(2) y – 1 = 0

y – 1 = 0 => y=1
as xy >0 => x>0

=> xy – y = x-1 . No other information related to x given
Insufficient

Answer: A

Luca1111111111111 · Answer

3 is a prime, so only 3*1 results in 3. 
(1) Therefore, x must be 3 and y must be 1 or the other way around. In either case, subtracting y would change the result to non-3. So, A is sufficient. 
(2) y equals 1, we have no information about x, so it is insufficient.

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If xy > 0, does xy y = 3? (1) xy = 3 (2) y 1 = 0

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