GMATPrep Arithmetic

[caramel3536]

If R = 1 + 2xy +x(squared)y(squared)
What is the value of xy
(1) R = 0
(2) x>0

Ans = A

[parallel_chase]

If R = 1 + 2xy +x(squared)y(squared)
What is the value of xy
(1) R = 0
(2) x>0

Ans = A

The answer is indeed A

R=1+2xy+x^2y^2 => (1+xy)^2

Statement I

R=0, therefore (1+xy)^2=0
xy=-1

Statement II
x>0

It does not gives us any specific value of x or y or R

Not Sufficient.


Hence A.

[caramel3536]

Thanks

[bhumika.k.shah]

R=1+2xy+x^2y^2 => (1+xy)^2

Statement I

R=0, therefore (1+xy)^2=0
xy=-1

Hi, could you explain me the boldfaced part???

[thephoenix]

R=1+2xy+x^2y^2 => (1+xy)^2

Statement I

R=0, therefore (1+xy)^2=0
xy=-1

Hi, could you explain me the boldfaced part???

sq of any non zero no. will be a non zero number only
since after squaring the no. is zero -----> the no. itself is zero---->1+xy=0---->xy=-1

[bhumika.k.shah]

sq of any non zero no. will be a non zero number only
since after squaring the no. is zero -----> the no. itself is zero---->1+xy=0---->xy=-1

Again this is what i wanted to learn. The concept. THanks

[HPengineer]

I solved this by saying X^2 x Y^2 = A

Then saying A^2 + 2A +1 = 0

(A + 1 ) (A +1)

A = -1 so XY = -1

Is this safe?

[anshumishra]

I solved this by saying X^2 x Y^2 = A

Then saying A^2 + 2A +1 = 0

(A + 1 ) (A +1)

A = -1 so XY = -1

Is this safe?

Yes, it is safe.
I guess you meant to write : xy = A. (not X^2*Y^2=A).

[HPengineer]

u got where i was going! Thanks!