Table of contents
- 0. Review of Algebra4h 16m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 6m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 19m
- 10. Combinatorics & Probability1h 45m
8. Conic Sections
Parabolas
Textbook Question
Find the vertex, focus, and directrix of the parabola with the given equation. Then graph the parabola. y^2 = 8x
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1
Rewrite the given equation \( y^2 = 8x \) in the standard form of a parabola. The standard form for a parabola that opens horizontally is \( (y - k)^2 = 4p(x - h) \).
Identify the values of \( h \), \( k \), and \( p \) by comparing \( y^2 = 8x \) with \( (y - k)^2 = 4p(x - h) \). Here, \( h = 0 \), \( k = 0 \), and \( 4p = 8 \).
Solve for \( p \) using the equation \( 4p = 8 \). This gives \( p = 2 \).
Determine the vertex of the parabola, which is at \( (h, k) = (0, 0) \).
Find the focus and directrix: The focus is \( (h + p, k) = (2, 0) \) and the directrix is the line \( x = h - p = -2 \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Parabola Definition
A parabola is a symmetric curve formed by the intersection of a cone with a plane parallel to its side. In algebra, parabolas can be represented by quadratic equations, typically in the form y^2 = 4px or x = ay^2. The orientation of the parabola (opening left, right, up, or down) depends on the equation's structure.
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Vertex of a Parabola
The vertex of a parabola is the point where it changes direction, representing either the maximum or minimum value of the quadratic function. For the equation y^2 = 8x, the vertex is located at the origin (0,0), which is the point of symmetry for the parabola. Understanding the vertex is crucial for graphing the parabola accurately.
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Focus and Directrix
The focus and directrix are key components that define a parabola's shape and position. The focus is a fixed point inside the parabola where all reflected lines converge, while the directrix is a line perpendicular to the axis of symmetry. For the equation y^2 = 8x, the focus is at (2,0) and the directrix is the line x = -2, which helps in accurately sketching the parabola.
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