解方程软件，自己做的，开源。GPL3。
懒得写中文文档。直接上英文README。

SOLVEQUAD README
A useful tool that collects information about a quadratic equation.
Input the a, b, c of a*x^2+b*X+c=0 then you will get some information.
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CREDITS
Koc Zhang zszth@126.com
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2011.06.10 v0.1
The first version. These functions are available:
Input the a, b, c of a*x^2+b*X+c=0;
Check a;
Get the shape (U or n);
Get the axis of symmetry;
Get the min or the max;
Get and check delta;
Get the real solutions.
TODOS
To make this form: a*(x+b)^2+c=0 available.
To get the min or max of a closed interval.
To input or display in rational number and try to keep the radical sign.
We hope to do some of these in the next version.
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http://www.koccn.net/work/
或者
http://code.google.com/p/solvequad/