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Old 2006-10-29, 19:21   #5
S485122
 
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Sep 2006
Brussels, Belgium

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Quote:
Originally Posted by Jacob Visser View Post
y=(-x+3+sqrt((x-3)2-4(x2-3x)))/2
and
y=(-x+3+sqrt((x-3)2-4(x2-3x)))/2
the determinant must be positive, thus (x-3)2-4(x2-3x)=-3x2+2x+3 >= 0
Miscutting and pasting and completely wrong calculation on my part :-(
(I had the values already and just needed to justify them ;-)

It should be
y=(-x+3+sqrt((x-3)2-4(x2-3x)))/2
and
y=(-x+3-sqrt((x-3)2-4(x2-3x)))/2

(x-3)2-4(x2-3x)=)=-3x2+6x+9
and this is non negative for x larger or equal to -1 and less or equal to +3.

As for:
Quote:
Originally Posted by Wacky View Post
But don't leave out the x=y part. As noted, the relationship holds for any integer k and x = y = k.
It was covered in my first sentence :
Quote:
Originally Posted by Jacob Visser View Post
the easy part is x=y and needs no explaining

Last fiddled with by S485122 on 2006-10-29 at 19:29
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