Chapter 13: Problem 30
Identify whether each equation, when graphed, will be a parabola, circle, ellipse, or hyperbola. Sketch the graph of each equation. \(x=y^{2}+4 y-1\)
Short Answer
Expert verified
The given equation represents a horizontally-opening parabola.
Step by step solution
01
Identify the equation form
Given the equation \(x = y^{2} + 4y - 1\), this needs to be analyzed to identify its form. It resembles the form of \(x = a(y - k)^2 + h\), which is a parabola that opens horizontally.
02
Recognize coefficients and complete the square
In the equation \(x = y^2 + 4y - 1\), we can complete the square for \(y\). This helps us rewrite it in vertex form. Start by dealing with \(y^2 + 4y\): \((y^2 + 4y) = (y+2)^2 - 4\).
03
Rewrite the equation in vertex form
Substitute \((y+2)^2 - 4\) back into the equation: \(x = (y+2)^2 - 4 - 1\). Simplifying gives \(x = (y+2)^2 - 5\). This confirms it's a parabola.
04
Determine the direction and vertex
Since the equation is \(x = (y+2)^2 - 5\), it's a horizontally-opening parabola. The vertex is at \((-5, -2)\).
05
Sketch the graph
Plot the vertex at \((-5, -2)\). Since it opens horizontally, draw the parabolic shape with the axis of symmetry parallel to the y-axis. It opens in the positive x-direction.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
Completing the square is a useful technique in algebra that helps transform a quadratic equation into a form that is easier to analyze, especially when identifying specific features like the vertex of a parabola. When given the equation \(x = y^2 + 4y - 1\), you first focus on the quadratic terms involving \(y\). Completing the square involves:
- Focusing on the expression \(y^2 + 4y\).
- Taking half of the coefficient of \(y\), which in this case is 4, resulting in 2, and then squaring it to get 4.
- Rewriting \(y^2 + 4y\) as \((y + 2)^2 - 4\).
Vertex Form
The vertex form of a parabolic equation is a reconceptualization that makes it simple to analyze and graph parabolas. It is generally written as \( x = a(y - k)^2 + h \) for parabolas opening horizontally, where \( (h, k) \) is the vertex of the parabola.When we rewrite \( x = y^2 + 4y - 1 \) by completing the square, we get \( x = (y + 2)^2 - 5 \). This equation is now in the vertex form.The benefits of having a parabola in vertex form include:
- Identifying the vertex directly; here it is \((-5, -2)\).
- Understanding the direction of the opening: this parabola opens horizontally because the \(y\)-terms are squared.
- Visualizing the parabola's graph becomes easier since the vertex is a key reference point.
Conic Sections
Conic sections are the curves obtained by intersecting a plane with a double-napped cone. The shape and nature of the conic depend on the angle of the intersection.In mathematics, four primary types of conic sections can occur:
- Circle: A conic section with all points equidistant from the center.
- Ellipse: An elongated circle formed when the plane cuts the cone at an angle to its base.
- Parabola: Formed when the plane is parallel to the side of the cone. This is the type relevant to our equation \(x = y^2 + 4y - 1\).
- Hyperbola: Created when the plane intersects both halves of the cone.