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by sanju09 » Tue May 11, 2010 2:58 am
colakumarfanta wrote:If x = 0 and x = sqrt(8xy-16y^2) , then, in terms of y, x = ?
A. - 4y
B. y/4
C. y
D. 4y
E. 4y^2

OA D
We can take 8 x y - 16 y^2 = 0 or 8 x y = 16 y^2 , but if x is already 0, y should also be 0 to hold the stem as true, and in that case, division by either x or y is not valid, and the question cannot be answered. I am not convinced with the contents supplied to work on, it's making me limcakumarthumsup, huh!
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
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User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Tue May 11, 2010 3:13 am
sanju09 wrote:
colakumarfanta wrote:If x = 0 and x = sqrt(8xy-16y^2) , then, in terms of y, x = ?
A. - 4y
B. y/4
C. y
D. 4y
E. 4y^2

OA D
We can take 8 x y - 16 y^2 = 0 or 8 x y = 16 y^2 , but if x is already 0, y should also be 0 to hold the stem as true, and in that case, division by either x or y is not valid, and the question cannot be answered. I am not convinced with the contents supplied to work on, it's making me limcakumarthumsup, huh!
And if x ≠ 0, then x^2 = 8 x y - 16 y^2

Or x^2 - 8 x y + 16 y^2 = 0

Or x^2 - 4 x y - 4 x y + 16 y^2 = 0

Or (x - 4 y) ^2 = 0

Or [spoiler]x = 4 y

D[/spoiler]
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
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