Re: Prob Solving - Help reqd

The answer option given are,
a) 2, b) 4, c) 8, d) 16, e) 32

Hi. If I copied the problem correctly, Mathematica shows that 'All'
solutions are valid. Each 'Solve had multiple solutions also.


equ = (2*(x + y)^2)/(2*(x - y)^2);

Solve[{equ == 2, x*y == 1}, {x, y}]

{x -> -1 - Sqrt[2], y -> 1 - Sqrt[2]}


Solve[{equ == 4, x*y == 1}, {x, y}]

{x -> -(1/Sqrt[3]), y -> -Sqrt[3]}


Solve[{equ == 16, x*y == 1}, {x, y}]

{x -> -Sqrt[3/5], y -> -Sqrt[5/3]}

--
Dana


"Robert Israel" <israel@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:rbisrael.20070430051920$6ecd@xxxxxxxxxxxxxxxxxxx
sathishvijay <sathish.vijayaraghavan@xxxxxxxxx> writes:

Hi All

I took a practice GMAT test from the prep files. I got the below
question and wasnt able to solve it. Please help me.

If xy = 1, what is the value of

{2* (x+y)^2} / {2* (x-y)^2}

The answer option given are,

a) 2, b) 4, c) 8, d) 16, e) 32

And they claim that correct answer is d) 16

Please let me know how to get this correct.

If that's really the question, all the above answers
are wrong. Try some random value of x, and y = 1/x.
You could get any number greater than 1 (assuming
x and y are supposed to be real).
--
Robert Israel israel@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada


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