Look at Math::Polynomial::Solve.

From the document..

# Find the roots of ax + b
  my @x1 = linear_roots($a, $b);

# Find the roots of ax**2 + bx +c
my @x2 = quadratic_roots($a, $b, $c);
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Artist

As an alternative to what has already been mentioned above, Math::GSL is also an option. It's a Perl API for calling the Gnu Scientific Library, an effort to provide a number of good-quality algorithms for numerical applications. Currently the Perl interface is far from complete in the sense that only a fraction of the GSL is accessible from Perl, but a polynomial solver happens to be available.

Hope this helps, -gjb-

Of course, some enterprising young programmer could (and should!) extend the interface and contribute back to the community. (Hint, hint!)

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

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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[x = - %I, x = %I]
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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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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