How do you solve the quadratic equation by completing the square: x^2-12x+20=0?

I found:
##x_1=10##
##x_2=2##
Rearrange your equation:
##x^2-12x=-20##
add and subtract ##36##;
##x^2-12xcolor(red)(+36-36)=-20##
##x^2-12x+36=-20+36##
so you can write:
##color(blue)((x-6)^2=16)##
square root both sides:
##x-6=+-sqrt(16)=+-4##
so you end up with two solutions:
##x_1=6+4=10##
##x_2=6-4=2##