It would be greate to write a module to encapsulate maxima, which is the old DOE MACSYMA. See the most excellent Maxima home page. It is a great program and runs on many platforms. It is maintained by William F. Schelter, and has source code, a nice install for windows, and rpms for linux. I have had success with all of these.

Your sample equation is nifty since the solution is a complex number. Maxima program:

solve([2*x*(-5*10*x)=100],[x])
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yields:

[x = - %I, x = %I]
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Where %I is maxima's notation for sqrt(-1) .

Maxima is massive overkill for your requirements, since it can also solve nasty problems such as the indefinite integral:

integrate(sin(x)*exp(x^2),x);
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or a relatively difficult problem in two variables:

solve([2*x^2+14*y+y^2=5,x*y+14*x+x^2=0],[x,y])
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Even though it is overkill, it is a good open-source problem-solver for easy algebra problems.

I have used Maxima for many real-world problems and also for teaching algebra. It is much better at algebra than I am, so I use it because I don't have the answer key for my textbook!

It should work perfectly the first time! - toma