Question

nothing

Answer 1

I'm not really sure, but I believe you could complete the square:
x^2-6x+9=-1
(x-3)^2=-1
x-3=I
x=3+i

Answer 2

x-3=i *

Answer 3

or you could use the quadratic formula for a equation of form \[ax^2+bx+c=0\]\[x=\frac{ -b \pm \sqrt{b^2-4ac} }{ 2a }\]