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Square root

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Square root

by fleurdelisse » Fri Apr 17, 2009 11:07 am
If x and y are both positive, which of the following myst be greater than 1/(sqrt(x+y))

I. sqrt(x+y)/2x
II. sqrtx+sqrty/(x+y)
III. sqrtx - sqrty/(x+y)
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by DanaJ » Fri Apr 17, 2009 1:36 pm
I have my doubts about this problem. Could you please double-check to see of it's written correctly? Of course, I might be missing smth...
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by dumb.doofus » Fri Apr 17, 2009 9:25 pm
IMO B

If I break it down, what we have to compare is:
a) x+y > 2x
b) root(x+y)*(root(x)+root(y)) > x+y
c) root(x+y)*(root(x)-root(y)) > x+y

If you choose values for x and y, 1,1 and 1,2 and 2,1, you'll see that only b stands out.
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