[tex]\bf y = x^2 - 3\implies y=1x^2+0x-3\qquad now
\\\\\\
\textit{vertex of a parabola}\\ \\
\begin{array}{llccll}
y=&1x^2&+0x&-3\\
&\uparrow &\uparrow &\uparrow \\
&a&b&c
\end{array}\qquad
\left(-\cfrac{{{ b}}}{2{{ a}}}\quad ,\quad {{ c}}-\cfrac{{{ b}}^2}{4{{ a}}}\right)[/tex]
so, the x-coordinate is [tex]\bf -\cfrac{{{ b}}}{2{{ a}}}[/tex]
