91影视

The given figure is

The bridge is 25 feet high at the highest point and the highest point is the vertex of the parabola. So, $y$-coordinate of vertex is 25.

The base is 30 feet wide. So, the point $(30,0)$represents the lower right side.

Because the bridges is symmetric, the vertex must fall halfway between the leftmost point $(0,0)$and the right most point $(30,0)$

Thus, $x$-coordinate of vertex is 15.

Now, we will set up the coordinate system and draw the parabola as shown below.

The equation of graph in standard form is $y=a{(x-h)}^2+k$

The vertex is $(h,k)=(15,25)$

So, the equation is $y=a{(x-15)}^2+25$

Solve the equation by substituting $x=0,y=0$as the graph is passing through the origin.

$$\begin{gathered} 0=a{(0-15)}^2+250=225a+25 \\ 225a=-25 \\ a=-\frac{1}{9} \end{gathered}$$

Using the obtained value, the equation is$y=-\frac{1}{9}{(x-15)}^2+25$