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variables

by naaga » Mon Feb 16, 2009 5:18 am
17. If x≠0 and x= sqrt 4xy- 4y^2 then, in terms of y, x=
(A) 2y

(B) y

(C) y/2

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

(E) –2y


folks help me out ...
thanks in advance
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by DanaJ » Mon Feb 16, 2009 6:08 am
I'm going to assume that you mean x = sqrt(4xy - 4y^2). Raise to the second power and you get that:
x^2 = 4xy - 4y^2. Now "send" everything to the left and you get:
x^2 - 4xy + 4y^2 = 0. This one is equivalent to (x - 2y)^2 = 0 or that x - 2y = 0. This makes x = 2y with answer A.
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