An excellent site which has an extensive collection of applets which will allow you to experiment / explore many topics you study in Mathematics is Ron Barrow’s WaldoMaths. Use this link for age 11-16 and this for ages 16-18.
Suppose you wish to practice factorising quadratics – you could use this applet.
Just move the sliders until you achieve the correct result. Note that you have the choice of practising with just positive numbers if you wish.
Each applet has full instructions and will give you links to related applets.
To learn Mathematics you need to do Mathematics. Exploring applets such as these will help you do just that!