check the picture below, that's the suspension bridge with supporting cables and traffic on it.
[tex]\bf \textit{ vertex of a vertical parabola, using coefficients}\\\\
\begin{array}{lccclll}
y = &{{ 0.1}}x^2&{{ -7}}x&{{ +150}}\\
&\uparrow &\uparrow &\uparrow \\
&a&b&c
\end{array}\qquad
\left(-\cfrac{{{ b}}}{2{{ a}}}\quad ,\quad {{ c}}-\cfrac{{{ b}}^2}{4{{ a}}}\right)[/tex]
[tex]\bf \left(-\cfrac{(-7)}{2(0.1)}~~,~~150-\cfrac{(-7)^2}{4(0.1)} \right)\implies \left( \cfrac{7}{0.2}~~,~~150-\cfrac{49}{0.4} \right)
\\\\\\
\left( 35~~,~~ 150-122.5\right)\implies (\stackrel{\textit{away from tower}}{35}~~,~~\stackrel{\textit{closest to road}}{27.5})[/tex]
