Chapter 7: Problem 66
Find an equation of a parabola that satisfies the given conditions. Horizontal axis, vertex \((-1,2),\) passing through \((2,3)\)
Short Answer
Expert verified
The equation is \((y - 2)^2 = \frac{1}{3}(x + 1)\).
Step by step solution
01
Identify the Equation Form
For a parabola with a horizontal axis, the standard form is expressed as \[(y - k)^2 = 4p(x - h)\] where \((h, k)\) is the vertex of the parabola. In this problem, the vertex is given as \((-1, 2)\).
02
Substitute the Vertex Coordinates
Insert the vertex coordinates \((-1, 2)\) into the standard form:\[(y - 2)^2 = 4p(x + 1)\].
03
Use Point to Solve for 'p'
The parabola passes through the point \((2, 3)\). Substitute \(x = 2\) and \(y = 3\) into the equation to find \(p\):\[(3 - 2)^2 = 4p(2 + 1)\]\[1 = 12p\]Solving for \(p\), you get \(p = \frac{1}{12}\).
04
Write the Equation
Plug the value of \(p\) back into the equation:\[(y - 2)^2 = \frac{4}{12}(x + 1)\]Simplifying, the equation of the parabola is:\[(y - 2)^2 = \frac{1}{3}(x + 1)\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex Form
Understanding the vertex form of a parabola is crucial when dealing with quadratic equations, especially when the parabola's orientation changes. This form is different based on the axis of symmetry it follows. For a parabola with a horizontal axis of symmetry, the vertex form of the equation is given as:
- \[(y - k)^2 = 4p(x - h)\]
- Vertex \( (h, k) \): This point indicates the peak or lowest point of the parabola, depending on its orientation.
- Focus Parameter \( p \): This determines the distance between the vertex and the focus, directly affecting the parabola's width.
Horizontal Axis
The horizontal axis defines a unique orientation of a parabola, which alters the typical "up" or "down" opening commonly seen in most introductory parabola discussions. When a parabola has a horizontal axis of symmetry, it opens to the right or left depending on the position of the focus relative to the vertex. This means the x-values affect the way the parabola stretches or compresses.
- In a horizontal orientation, the positions of the x and y terms in the formula are switched from the typical vertical forms you might know.
- Imagine the U-shape of a vertical parabola, but lying on its side. It's distinctive, as the y-values now determine the vertex horizontally.
- This kind of parabola is characterized by having its squared term as \( (y - k)^2 \), which signifies y-values being pivotal in stretching the shape horizontally.
Coordinate Geometry
Coordinate geometry is a powerful tool in understanding the properties and equations of shapes like parabolas in a given plane. By using coordinates, you can precisely define the shape, orientation, and size of geometric figures, essential for solving problems in algebra and calculus.
- Point-Slope Relationships: The coordinates of the vertex and other points (like those on the parabola) help in forming equations that reflect real-world shapes.
- Substitution Method: By substituting values into the equation, such as finding \(p\) when given an extra point, you solidify the parabola's equation with precision.
- Visualizing Movement: Understanding coordinates means you can move shapes around a graph seamlessly without losing their structural integrity, which is vital for solving geometric transformations.