MAT is a free, open-source app that allows you to solve:
Second Grade Equations
Determinants
Systems of Equations
Roots of Polinomials
Statistics
Triangles
And is available in English, Spanish and Catalan.
MAT source code:
https://github.com/TomasOrtega/MAT
GNU GPL-2 license:
http://gnu.org/licenses/old-licenses/gpl-2.0.html
MAT author: Tomàs Ortega