Find the vertex, focus, and directrix of each parabola with the given equation. Then graph the parabola. (y + 3)2 = 12(x + 1)
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- 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 47
Textbook Question
Convert each equation to standard form by completing the square on x or y. Then find the vertex, focus, and directrix of the parabola. Finally, graph the parabola. x2 + 6x - 4y + 1 = 0
Verified step by step guidance1
Start by rewriting the given equation \(x^2 + 6x - 4y + 1 = 0\) to isolate the \(y\) terms on one side. Move all terms except those involving \(y\) to the other side: \(-4y = -x^2 - 6x - 1\).
Divide both sides of the equation by \(-4\) to solve for \(y\): \(y = \frac{1}{4}x^2 + \frac{3}{2}x + \frac{1}{4}\).
To complete the square for the \(x\) terms, focus on the quadratic expression \(\frac{1}{4}x^2 + \frac{3}{2}x\). Factor out \(\frac{1}{4}\) from the \(x\) terms: \(y = \frac{1}{4}(x^2 + 6x) + \frac{1}{4}\).
Complete the square inside the parentheses: take half of the coefficient of \(x\) (which is 6), square it, and add and subtract that value inside the parentheses. Half of 6 is 3, and \$3^2 = 9\(. So, write \)x^2 + 6x + 9 - 9\( inside the parentheses: \)y = \frac{1}{4}((x + 3)^2 - 9) + \frac{1}{4}$.
Simplify the equation by distributing \(\frac{1}{4}\) and combining constants: \(y = \frac{1}{4}(x + 3)^2 - \frac{9}{4} + \frac{1}{4}\). This gives the standard form of the parabola, from which you can identify the vertex, focus, and directrix.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Completing the Square
Completing the square is a method used to rewrite quadratic expressions in the form (x - h)^2 = k, which helps convert equations into standard form. This involves adding and subtracting a constant to create a perfect square trinomial, making it easier to identify key features of conic sections like parabolas.
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Solving Quadratic Equations by Completing the Square
Standard Form of a Parabola
The standard form of a parabola's equation reveals its vertex and orientation. For a parabola opening vertically, it is written as (x - h)^2 = 4p(y - k), where (h, k) is the vertex and p relates to the distance between the vertex and the focus or directrix.
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Parabolas as Conic Sections
Vertex, Focus, and Directrix of a Parabola
The vertex is the parabola's turning point, the focus is a fixed point inside the parabola, and the directrix is a line outside it. The parabola is the set of points equidistant from the focus and directrix, and these elements are essential for graphing and understanding its shape.
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Horizontal Parabolas Example 1
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