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PS root question

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PS root question

by ccarson » Fri Aug 31, 2007 5:55 am
17. If x doesn't equal zero and x= root(4xy-4y^2), then, in terms of y, x=

A) 2y

B) y

C) y/2

D)(-4y^2)/(1-4y)

E) -2y

Answer is A. I can find the answer by subbing-in but having more trouble finding it algebraicly. Can anyone help?

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by agps » Fri Aug 31, 2007 6:48 am
x=sqrt(4xy-4y^2)
if you square both sides you get
x^2=4xy-4y^2
x^2-4xy+4y^2=0
this is the same as (x-2y)^2=0
therefore x-2y=0
x=2y

Answer is A.
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by kajcha » Fri Aug 31, 2007 7:43 am
Agree with the explanation Ans A
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