In The Xy Plane A Parabola Has Vertex 9 -14

Exploring Parabolas: A Deep Dive into the Equation with Vertex (9, -14)

This article delves into the fascinating world of parabolas, focusing specifically on a parabola with its vertex located at the point (9, -14) in the xy-plane. We'll explore its equation, properties, and how to manipulate its characteristics. Understanding parabolas is crucial in various fields, including mathematics, physics, and engineering, where they model projectile motion, antenna design, and reflector shapes. This exploration will cover the fundamental concepts and provide a comprehensive understanding of this conic section.

I. Understanding Parabolas: Basic Definitions and Concepts

A parabola is a U-shaped curve that is defined as the set of all points in a plane that are equidistant from a fixed point (the focus) and a fixed straight line (the directrix). The parabola's symmetry is defined by its axis of symmetry, a line that divides the parabola into two mirror images. The point where the parabola intersects its axis of symmetry is called the vertex.

The general equation of a parabola that opens vertically is given by:

y = a(x - h)² + k

where:

• (h, k) represents the coordinates of the vertex.
• 'a' determines the parabola's shape and direction. If 'a' is positive, the parabola opens upwards; if 'a' is negative, it opens downwards. The absolute value of 'a' affects the parabola's width; a larger |a| results in a narrower parabola, while a smaller |a| results in a wider one.

II. The Parabola with Vertex (9, -14)

Knowing the vertex is (9, -14), we can substitute h = 9 and k = -14 into the general equation:

y = a(x - 9)² - 14

This equation represents a family of parabolas, all sharing the same vertex (9, -14) but differing in their width and direction (upward or downward) depending on the value of 'a'.

III. Determining the Value of 'a'

To pinpoint a specific parabola within this family, we need additional information. This information might take the form of:

• Another point on the parabola: If we know the coordinates of another point (x, y) that lies on the parabola, we can substitute these values into the equation y = a(x - 9)² - 14 and solve for 'a'.

• The focus or directrix: The focus and directrix are related to the value of 'a' through a specific formula. The distance from the vertex to the focus (and from the vertex to the directrix) is given by |1/(4a)|. Knowing the focus or directrix allows us to calculate 'a'.

Let's illustrate with an example. Suppose another point on the parabola is (10, -13). Substituting this into the equation:

-13 = a(10 - 9)² - 14 -13 = a - 14 a = 1

Therefore, the equation of the parabola passing through (10, -13) and having a vertex at (9, -14) is:

y = (x - 9)² - 14 This parabola opens upwards.

Now let's consider another example. Suppose the focus of the parabola is at (9, -13.75). The distance between the vertex (9, -14) and the focus (9, -13.75) is 0.25. Since the distance from the vertex to the focus is |1/(4a)|, we have:

0.25 = |1/(4a)| 1 = |1/(a)| a = 1

This confirms the previous result.

IV. Exploring Different 'a' Values and their Effects

Let's examine how different values of 'a' affect the shape of our parabola:

• a = 1: The parabola opens upwards, with a moderate width. This is the case in our previous example.

• a = 2: The parabola opens upwards but is narrower than when a = 1.

• a = 0.5: The parabola opens upwards and is wider than when a = 1.

• a = -1: The parabola opens downwards, with a moderate width. It's a reflection of the a = 1 parabola across the horizontal line y = -14.

• a = -2: The parabola opens downwards and is narrower than when a = -1.

• a = -0.5: The parabola opens downwards and is wider than when a = -1.

V. Other Forms of the Parabola Equation

While the standard form y = a(x - h)² + k is commonly used, parabolas can also be represented by other equations:

• x = a(y - k)² + h: This represents a parabola that opens horizontally. If 'a' is positive, it opens to the right; if 'a' is negative, it opens to the left.

• Implicit Form: The parabola can also be expressed in an implicit form, which is a more general equation involving both x and y terms. However, this form is less convenient for finding the vertex and other key features.

VI. Applications of Parabolas

Parabolas find practical applications in various fields:

• Physics: The trajectory of a projectile (neglecting air resistance) follows a parabolic path.

• Engineering: Parabolic reflectors are used in antennas, satellite dishes, and telescopes to focus signals or light.

• Architecture: Parabolic arches are often used in bridge construction.

• Optics: Parabolic mirrors are employed in optical systems for their ability to focus parallel rays of light to a single point.

VII. Solving Problems Involving Parabolas

Let's look at some example problems:

Problem 1: Find the equation of the parabola with vertex (9, -14) that passes through the point (11, -10).

Solution: Substitute h = 9, k = -14, x = 11, and y = -10 into the equation y = a(x - h)² + k:

-10 = a(11 - 9)² - 14 -10 = 4a - 14 4a = 4 a = 1

Therefore, the equation is y = (x - 9)² - 14.

Problem 2: A parabola has vertex (9, -14) and focus (9, -13). Find its equation.

Solution: The distance from the vertex to the focus is 1. Since this distance is equal to |1/(4a)|, we have:

1 = |1/(4a)| 4a = 1 or 4a = -1 a = 1/4 or a = -1/4

Since the focus is above the vertex, the parabola opens upwards, so a = 1/4. The equation is y = (1/4)(x - 9)² - 14.

VIII. Frequently Asked Questions (FAQ)

Q1: What is the axis of symmetry of the parabola with vertex (9, -14)?

A1: The axis of symmetry is a vertical line passing through the vertex. Its equation is x = 9.

Q2: How can I find the x-intercepts of a parabola?

A2: To find the x-intercepts, set y = 0 and solve the resulting quadratic equation for x.

Q3: How can I find the y-intercept of a parabola?

A3: To find the y-intercept, set x = 0 and solve for y.

Q4: What is the difference between a parabola and other conic sections (ellipse, hyperbola)?

A4: Parabolas, ellipses, and hyperbolas are all conic sections, meaning they can be formed by intersecting a cone with a plane. They differ in their shapes and defining properties. Parabolas have one focus and one directrix, ellipses have two foci, and hyperbolas have two foci and two branches.

Q5: Can a parabola have more than one vertex?

A5: No, a parabola has only one vertex, which is the point where the curve turns.

IX. Conclusion

Understanding parabolas, especially those with a given vertex like the one discussed here, requires a solid grasp of their equation, properties, and the relationship between their parameters. This article has provided a comprehensive overview, covering various aspects from fundamental definitions to practical applications and problem-solving. By mastering these concepts, you'll be well-equipped to tackle more complex problems involving parabolas in various mathematical and scientific contexts. Remember, the key is to understand the interplay between the vertex, the value of 'a', and the resulting shape of the parabola. With practice and further exploration, you'll find that these seemingly simple curves hold a wealth of mathematical beauty and practical utility.