You can put this solution on YOUR website! f(x)=x^2-2x-4
x=(2+-sqrt[-2^2-4*1*-4])/2*1
x=(2+-sqrt[4+16])/2
x=(2+-sqrt20)/2
x=(2+-4.472)/2
x=(2+4.72)/2
x=6.72/2
x=3.36 ans.
x=(2-4.72)/2
x=-2.72/2
x=-1.36 ans. (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, x^2 -2x -4).