The quadratic formula
[tex]x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}[/tex]
for equation
[tex]ax^2+bx+c=0[/tex]
In the given case
[tex]x^2-2x-4=0[/tex]
a=1
b=-2
c=-4
Substitute in the quadratic equation
[tex]x=\frac{-(-2)\pm\sqrt{(-2)^2-4(1)(-4)}}{2(1)}[/tex]
[tex] =\frac{2\pm\sqrt{4+16}}{2}[/tex]
[tex] = 1\pm\sqrt{5}[/tex]
