Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 521: 9

$x=6$

Comparing $x^{2}-12x+36=0$ with $ax^{2}+bx+c=0$, we get $a=1$, $b=-12$ and $c=36$. The quadratic formula is $x=\frac{-b \pm \sqrt {b^{2}-4ac}}{2a}$ Substituting the values, we get $x=\frac{-(-12) \pm \sqrt {(-12)^{2}-4(1)(36)}}{(2)(1)}=6$