Download GeoGebra, to practise mathematics and geometry
GeoGebra is a dynamic mathematics freeware for schools; it joins geometry, algebra and calculus.
On the one hand, GeoGebra is an interactive geometry system. You can do constructions with points, vectors, segments, lines, conic sections as well as functions and change them dynamically afterwards.
On the other hand, equations and coordinates can be entered directly. Thus, GeoGebra has the ability to deal with variables for numbers, vectors and points, find derivatives and integrals of functions and offer commands like Root or Extremum.
These two views are characteristic of GeoGebra: an expression in the algebra window corresponds to an object in the geometry window and vice versa.