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# What is the value of 3^-(x + y) / 3^-(x - y)? (1) x = 2 (2)

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Senior Manager
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What is the value of 3^-(x + y) / 3^-(x - y)? (1) x = 2 (2) [#permalink]  10 Oct 2008, 06:26
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What is the value of 3^-(x + y) / 3^-(x - y)?
(1) x = 2
(2) y = 3
VP
Joined: 30 Jun 2008
Posts: 1046
Followers: 11

Kudos [?]: 357 [0], given: 1

Re: DS [#permalink]  10 Oct 2008, 07:10
vksunder wrote:
What is the value of 3^-(x + y) / 3^-(x - y)?
(1) x = 2
(2) y = 3

The question stem needs simplification

3^-(x + y) / 3^-(x - y) = 3^ -(x+y) + (x-y) = 3^(-x+y+x+y) = 3^2y

All we need to know is the value of y. Which only statement 2 provides.

So I go for B
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Senior Manager
Joined: 10 Mar 2008
Posts: 375
Followers: 4

Kudos [?]: 102 [0], given: 0

Re: DS [#permalink]  10 Oct 2008, 08:53
Thanks for your input amitdgr. OA - B

I'm messing up the calculation some where and I cant figure out why I end up with 3^-2y and not 3^2y. Here is how I've solved the equation:

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

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

3^(-x-y) * 3^-(-x+y)

3^(-x-y) * 3^(x-y)

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

3^-x-y+x-y

3^ -2y

Thanks!
Manager
Joined: 15 Apr 2008
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Re: DS [#permalink]  10 Oct 2008, 09:01
vksunder wrote:
What is the value of 3^-(x + y) / 3^-(x - y)?
(1) x = 2
(2) y = 3

I also got B

1/3^(x+y)*3^-x+y=1/3^2y

since statement 2 gives y=3, the answer can be known.
VP
Joined: 30 Jun 2008
Posts: 1046
Followers: 11

Kudos [?]: 357 [0], given: 1

Re: DS [#permalink]  10 Oct 2008, 09:28
vksunder wrote:
Thanks for your input amitdgr. OA - B

I'm messing up the calculation some where and I cant figure out why I end up with 3^-2y and not 3^2y. Here is how I've solved the equation:

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

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

3^(-x-y) * 3^-(-x+y)

3^(-x-y) * 3^(x-y)

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

3^-x-y+x-y

3^ -2y

Thanks!

In fact, You got it right. I got it wrong
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Re: DS   [#permalink] 10 Oct 2008, 09:28
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