x^2-12x+59=0
Using quadratic formula.
[tex]x_{1,\:2}=\frac{-b\pm \sqrt{b^2-4ac}}{2a} \\
[/tex]
Here
a=1 , b=-12 and c=59
Put values in formula.
[tex]x=\frac{-\left(-12\right)\pm \sqrt{\left(-12\right)^2-4\cdot \:1\cdot \:59}}{2\cdot \:1} \\
[/tex]
Simplify
[tex]x= \frac{12\pm \sqrt{144-236} }{2} [/tex]
[tex]x=6\pm \sqrt{23}i [/tex]
[tex]Answer: \ 6 \pm \sqrt{23}i [/tex]