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3^-(x + y) / 3^-(x - y)?

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Source: — Data Sufficiency |
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by superdesi2100 » Fri Jan 22, 2010 10:41 am
3^-(x+y)/3^-(x-y) = 3^-(x+y)/3^(-x+y)
=3^-(x+y)-(-x+y)
=3^-x-y+x-y
=3^-2y

IMO The answer should be B.
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by bhumika.k.shah » Fri Jan 22, 2010 10:51 am
^-(x+y)/3^-(x-y)
= 3^-(x+y)-(x-y) ....((eg. t^-4 = 1/t^4))
=3^-x-y-x+y ....((opening the brackets))
=3^-2x....((-y+y gets cancelled))
Therefore ,
Statement I itself is sufficient since we only require the value of x

IMO A

:-)

finally racking my brains did help :-D
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by inetcleopatra » Fri Jan 22, 2010 12:19 pm
In this equation, the x cancels out not y. So, the answer should be B. We need the value of y to solve not x.

To illustrate,

3^ -(x+y) /3^ -(x-y)
{1/3^(x+y)} / {1/3^(x-y)}
3^(x-y) / 3^(x+y)
3^(x-y)-(x+y)
3^x-y-x-y
3^-2y
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by bhumika.k.shah » Fri Jan 22, 2010 12:22 pm
hahhha . yup i agree. sowree did it the other way . 1 kudos to you for this :-)
inetcleopatra wrote:In this equation, the x cancels out not y. So, the answer should be B. We need the value of y to solve not x.

To illustrate,

3^ -(x+y) /3^ -(x-y)
{1/3^(x+y)} / {1/3^(x-y)}
3^(x-y) / 3^(x+y)
3^(x-y)-(x+y)
3^x-y-x-y
3^-2y
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by mehravikas » Fri Jan 22, 2010 6:37 pm
Answer should be B. as we can cancel out x. so we need the value of y.
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