Algebra 2 - Standard form of a quadratic function

1. A field goal kicker discussed his performance with this coach. Based on the coach’s data, the kicker usually kicks the ball so it reaches a maximum height of 50 yards
after it has traveled 25 yards down the field. What is the equation, in standard form, of the kick? Round your answer to the nearest hundredth


2. If the goal posts are 10 yards high, what is the minimum and maximum distance that his kick will make it over the goalpost? Round your answer to the nearest hundredth

Respuesta :

Using quadratic function concepts, it is found that:

1) The equation is [tex]y = -0.08x^2 + 4x[/tex]

2) The minimum distance is of 2.64 yards, and the maximum is of 47.36 yards.

A quadratic equation has the following format:

[tex]y = ax^2 + bx + c[/tex]

In this problem:

  • The ball was kicked from the ground, thus [tex]y(0) = 0[/tex], which means that c = 0.

Item 1:

The vertex is: [tex]V(x_v,y_v)[/tex], in which:

[tex]x_v = -\frac{b}{2a}[/tex]

[tex]y_v = -\frac{\Delta}{4a} = -\frac{b^2 - 4ac}{4a}[/tex]

In this problem, it is (25,50). Thus:

[tex]-\frac{b}{2a} = 25[/tex]

[tex]-b = 50a[/tex]

[tex]b = -50a[/tex]

[tex]-\frac{b^2 - 4ac}{4a} = 50[/tex]

[tex]-b^2 = 200a[/tex]

[tex]-(50a)^2 = 200a[/tex]

[tex]-2500a^2 - 200a = 0[/tex]

[tex]200a(-12.5a - 1) = 0[/tex]

Then, as [tex]a \neq 0[/tex]

[tex]a = -\frac{1}{12.5} = -0.08[/tex]

[tex]b = -50a = -50(-0.08) = 4[/tex]

Thus, the equation, in standard form, is:

[tex]y = -0.08x^2 + 4x[/tex]

Item 2:

The distances are the values of x for which:

[tex]y = 10[/tex]

Then

[tex]-0.08x^2 + 4x = 10[/tex]

[tex]-0.08x^2 + 4x - 10 = 0[/tex]

Which is a quadratic equation with [tex]a = -0.08, b = 4, c = -10[/tex]. Then:

[tex]\Delta = 4^2 - 4(-0.08)(-10) = 12.8[/tex]

[tex]x_{1} = \frac{-4 + \sqrt{12.8}}{2(-0.08)} = 2.64[/tex]

[tex]x_{2} = \frac{-4 - \sqrt{12.8}}{2(-0.08)} = 47.36[/tex]  

The minimum distance is of 2.64 yards, and the maximum is of 47.36 yards.

A similar problem is given at https://brainly.com/question/24713268