This is a website with all tools needed for solving quadratic equation/function.
Follow this link: http://www.hostsrv.com/webmab/app1/MSP/quickmath/02/pageGenerate?site=quickmath&s1=equations&s2=quadratics&s3=basic [2]
Another good website: http://www.mathsisfun.com/quadratic-equation-solver.html [3]
Links:
[1] http://www.yuptutor.com/files/u1/tutoring_tools/170.gif
[2] http://www.hostsrv.com/webmab/app1/MSP/quickmath/02/pageGenerate?site=quickmath&s1=equations&s2=quadratics&s3=basic
[3] http://www.mathsisfun.com/quadratic-equation-solver.html