Question 430697
You solved it
{{{x^2-12x+36=0}}}
(1) {{{ (x - 6)^2 = 0 }}}
This is called a double root. 
The graph touches the x-axis in one place
What value of {{{x}}} makes (1) true?
{{{x = 6}}} makes it true. That's the solution.
Here's the graph:
{{{ graph( 400, 400, -10, 10, -10, 10, x^2 - 12x + 36) }}}