The dome over the town hall has a parabolic shape. I measure 48 m across and rises 12 m at its center. Determine the quadratic equation that models the shape of the parabola.

I have learned the formula y = a(x-s)(x-t).

User Icon for bobpursley bobpursley answered
6 years ago

so one side is at zero, and at 48m, it comes to zero again.

y=a(x)(x-48)
and at x=24 (half way across), y=12
12=a(24)(-24)
solve for a ( I get in my head -1/48)

User Icon for Explain Bot Explain Bot answered
11 months ago

To determine the quadratic equation that models the shape of the parabola, we need to find the values of a, s, and t in the equation y = a(x - s)(x - t).

Given that the dome has a parabolic shape and the equation y = a(x - s)(x - t) is factored form, we can use the information provided to determine the values of s and t.

From the measurements given, we know that the parabolic dome has a width of 48 m, which means the distance from one side to the other is 48 m. In the factored form of the equation, the difference between s and t represents the width of the parabola.

Since the width is 48 m, we can write:

t - s = 48

We also know that the parabola rises 12 m at its center. The x-coordinate of the vertex represents the center of the parabola, and at this point, the y-coordinate is the maximum or minimum value of the parabola. In this case, the center is the vertex, and the maximum value is 12 m.

Using the vertex form of a parabola, which is y = a(x - h)^2 + k, we can determine the vertex of the parabola by using the values from the given measurements:

h = (s + t)/2 = (s + (s + 48))/2 = (2s + 48)/2 = s + 24

k = 12

Substituting these values into the vertex form, we have:

y = a(x - (s + 24))^2 + 12

Simplifying this equation, we get:

y = a(x - s - 24)^2 + 12

Now we have the parabolic equation in vertex form, and we can determine the values of a, s, and t by comparing this equation to the factored form equation y = a(x - s)(x - t):

s + 24 = t
12 = 24^2a

From the first equation, we can solve for t:

t = s + 24

Substituting this back in the factored form equation, we have:

48 = 48^2a

Now we can solve for a:

48^2a = 48
a = 1/(48^2)

Finally, substituting the values of a, s, and t back into the factored form equation, we get the final quadratic equation that models the shape of the parabola:

y = 1/(48^2)(x - s)(x - t)