Practice Exam 1 - GMAT Prep - Algebra

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Practice Exam 1 - GMAT Prep - Algebra

by lucas211 » Wed May 25, 2016 4:22 pm
Hello BTG

Would appreciate some help on the following question.


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Thanks

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by Brent@GMATPrepNow » Wed May 25, 2016 4:27 pm
if xy=1 then what is the value of 2^(x+y)²/ 2^(x-y)²

1)2
2) 4
3) 8
4) 16
5) 32
2^(x+y)²/ 2^(x-y)² = 2^(x² + 2xy + y²)/ 2^(x² - 2xy + y²)
= 2^(4xy) [after we subtract exponents]
= 2^4 [since xy = 1]
= 16
= D

RELATED RESOURCE (video)
- Laws of exponents - part I: https://www.gmatprepnow.com/module/gmat ... video/1025

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GMAT/MBA Expert

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by Brent@GMATPrepNow » Wed May 25, 2016 4:31 pm
if xy=1 then what is the value of 2^(x+y)²/ 2^(x-y)²

1)2
2) 4
3) 8
4) 16
5) 32
Alternate Approach.

Since we're told that xy = 1, let's lets x = 1 and y = 1
We get:
2^(x+y)²/ 2^(x-y)² = 2^(1+1)²/ 2^(1-1)²
= 2^(2)²/2^(0)²
= 2�/2�
= 16/1
= 16
= D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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