x^2-2x-5=0
x^2-2x=5
x^2-2x+1=6
(x-1)^2=6
x-1=±√6
x1=√6+1
x2=-√6+1
3x^2+2x-1=0
3x^2+2x=1
x^2+2/3x=1/3
x^2+2/3x+1/9=1/3+1/9
(x+1/3)^2=4/9
x+1/3=±2/3
x1=1/3,x2=-1