well, the squared varaible is the "x", that means is a vertical parabola, so the axis of symmetry, will be x = "the x-coordinate of the vertex", whatever that coordinate happens to be, so let's check using the coefficients.
[tex]\bf \textit{ vertex of a vertical parabola, using coefficients}\\\\
\begin{array}{llccll}
y = &{{ 2}}x^2&{{ +8}}x&{{ +3}}\\
&\uparrow &\uparrow &\uparrow \\
&a&b&c
\end{array}\qquad
\left(-\cfrac{{{ b}}}{2{{ a}}}\quad ,\quad {{ c}}-\cfrac{{{ b}}^2}{4{{ a}}}\right)
\\\\\\
\left( -\cfrac{8}{2(2)}~~,~~ 3-\cfrac{8^2}{4(2)} \right)[/tex]
