Question 981868
You are looking to Complete The Square.  Learn to do that here:  <a href="http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev">http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev</a>.


The value to choose will be {{{(6/2)^2=9}}} to make a full square trinomial in the expression.


{{{x^2-6x+12}}}
{{{x^2-6x+9-9+12}}}
{{{(x^2-6x+9)-9+12}}}
{{{(x-3)^2-9+12}}}
{{{highlight((x-3)^2+3)}}}


If you really want in the form you specified, {{{(x+(-3))^2+3}}}.