What is the check for x^2-5x+6=0 by completing the square

$$\\x^2-5x+6=0\\ x^2-5x=-6\\ x^2-5x+(5/2)^2=-6+(5/2)^2\\ x^2-5x+25/4=-6+25/4\\ (x-5/2)^2=1/4\\\\ x-2.5=\pm 0.5\\ x=2.5\pm 0.5\\ x=3\qquad or \qquad x=2$$

check by substitution

$${{\mathtt{3}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{3}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}} = {\mathtt{0}}$$    true

$${{\mathtt{2}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}} = {\mathtt{0}}$$    true