If xy = 1

s_raizada · Posted: Thu Jun 12, 2008 2:04 pm Post subject: If xy = 1

If xy = 1, what is the value of (2(x + Y)^2)/(2(x - Y)^2)??

babachal · Posted: Thu Jun 12, 2008 3:23 pm Post subject:

Hey, can you give us full question?

netigen · Posted: Thu Jun 12, 2008 3:38 pm Post subject:

Question is what is the value of

2^(x + Y)^2)/2^(x - Y)^2

egybs · Posted: Thu Jun 12, 2008 4:02 pm Post subject:

ahhhh.. in that case it's easy!

2^(x+y)^2 / 2^(x-y)^2

2^((x+y)^2 - (x-y)^2)

2^(x^2 + 2xy + y^2 - x^2 + 2xy - y^2)

2^(4xy)

which as we know is equal to 2^4... so 16.

babachal · Posted: Thu Jun 12, 2008 4:17 pm Post subject:

egybs, you did mistake in the last step

2^(x^2+2xy+y^2-x^2+2xy-y^2)+2^4xy=2^4=16

egybs · Posted: Thu Jun 12, 2008 4:20 pm Post subject:

oops! yep. i did.

s_raizada · Posted: Fri Jun 13, 2008 1:36 am Post subject:

Hi guys,
question is not what you are calculating. See the screenshot of the question and it is form GMAT prep

AleksandrM · Posted: Fri Jun 13, 2008 9:19 am Post subject:

Undifined or 25/9????? Confused

egybs · Posted: Fri Jun 13, 2008 9:32 am Post subject:

Can you give us the answer options...

Ian Stewart · Posted: Fri Jun 13, 2008 11:23 am Post subject:

As has been posted elsewhere, there's a typo in the question itself. The solution posted above by netigen, with the x and y terms in the exponents, presented the question in the way it's supposed to be written.

GMAT dreamer · Posted: Tue Nov 18, 2008 12:16 pm Post subject:

We can make things simpler...
If xy=1; it tells that x=1 and y=1, right?

so, 2^(1+1)^2/2^(1-1)^2=
2^2^2/2^0^2=
2^4/2^0=
16/1= 16

Very simple we put numbers.

cramya · Posted: Tue Nov 18, 2008 3:40 pm Post subject: