We have the following:
[tex]\begin{gathered} x^2-6x+9=4 \\ \end{gathered}[/tex]solving by the square root property
[tex]\begin{gathered} x^2-6x+9=4 \\ x^2-6x+9-9=4-9 \\ x^2-6x=-5 \\ x^2+2ax+a^2=\mleft(x+a\mright)^2 \\ 2ax=-6x \\ 2a=-6\rightarrow a=-3 \\ x^2-6x+(-3)^2=-5+(-3)^2 \\ (x-3)^2=-5+(-3)^2 \\ (x-3)^2=-5+9 \\ x-3=\pm\sqrt[]{4} \\ x=\sqrt[]{4}+3=2+3=5 \\ x=-\sqrt[]{4}+3=-2+3=1 \end{gathered}[/tex]