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GRE Algebra (Select One or More) http://www.800score.com/forum/viewtopic.php?f=12&t=2761 
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Author:  questioner [ Sat Feb 25, 2012 4:05 pm ] 
Post subject:  GRE Algebra (Select One or More) 
If 20 – √x = 11, then what are possible values of x? 81, 9, 3, 9, 81 The correct answer is 81. Let's solve the equation 20 – √x = 11 by combining and rearranging. We get 9 = √x. Squaring both sides results in 81 = x, and this is the only value that x can take on. Thus, only answer 81 will be correct.  9 squared is also 81 is it not? 
Author:  Gennadiy [ Sat Feb 25, 2012 4:13 pm ] 
Post subject:  Re: t.4, s.4, qt.10: equations, radicals 
Quote: 9 squared is also 81 is it not? (9)² = 81 indeed, but the question is the inverse one.√x = 9, NOT x² = 81. 
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