In Exercises 1–4, find the focus and directrix of each parabola with the given equation. Then match each equation to one of the graphs that are shown and labeled (a)–(d). x^2 = 4y
Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
8. Conic Sections
Parabolas
Problem 9
Textbook Question
Find the focus and directrix of the parabola with the given equation. Then graph the parabola. x2 = 12y
Verified step by step guidance1
Identify the form of the given parabola equation. The equation is \(x^2 = 12y\), which matches the standard form of a vertical parabola: \(x^2 = 4py\), where the vertex is at the origin \((0,0)\) and the parabola opens upward if \(p > 0\) or downward if \(p < 0\).
Compare the given equation \(x^2 = 12y\) with the standard form \(x^2 = 4py\) to find the value of \(p\). Set \$4p = 12\(, then solve for \)p$.
Use the value of \(p\) to determine the focus of the parabola. For a parabola in the form \(x^2 = 4py\), the focus is located at \((0, p)\).
Find the equation of the directrix. The directrix is a horizontal line given by \(y = -p\) for this form of parabola.
Summarize the results: the vertex is at the origin \((0,0)\), the focus is at \((0, p)\), and the directrix is the line \(y = -p\). Use these to sketch the parabola, noting it opens upward since \(p\) is positive.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Standard Form of a Parabola
A parabola can be expressed in standard form as x² = 4py or y² = 4px, where p represents the distance from the vertex to the focus and directrix. Recognizing the equation's form helps identify the parabola's orientation and key features.
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Focus and Directrix of a Parabola
The focus is a fixed point inside the parabola, and the directrix is a line outside it, both equidistant from the vertex. For x² = 4py, the focus is at (0, p) and the directrix is the line y = -p, which guide the parabola's shape.
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Graphing a Parabola
Graphing involves plotting the vertex, focus, and directrix, then sketching the curve that is equidistant from the focus and directrix. Understanding symmetry and the parabola's opening direction (upward or downward) is essential for accurate graphing.
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