Eigenmath computer algebra system
The lightweight and powerful CAS now is ported to Android.
Perhaps you know it from the others versions for: windows, mac, ppc and nds.
The system was designed for the manipulation of symbolic algebraic expressionsand is powerful like a scientific calculator.
Some features:
Simplification to the smallest possible expression.
Solution of linear equations
Programmable.
Differentiation.
Indefinite and definite integration, including multidimensional integrals.
Matrix operations including products, inverses, etc.
Opcional and for a better input method install the math keyboard, its free:
https://play.google.com/store/search?q=com.eigenmath.android.mathkeyboard
See the documentation included.