Chapter 10: Problem 54
Write an equation of the hyperbola that satisfies each set of conditions. vertices \((6,-6)\) and \((0,-6),\) foci \((3 \pm \sqrt{13},-6)\)
Short Answer
Expert verified
The equation of the hyperbola is \(\frac{(x-3)^2}{9} - \frac{(y+6)^2}{4} = 1.\)
Step by step solution
01
Determine the Orientation
The vertices are given as (6,-6) and (0,-6), which means the hyperbola's vertices lie along the x-axis because the y-coordinate is the same for both. Therefore, the hyperbola opens horizontally. The standard equation of a hyperbola that opens horizontally is \[(x-h)^2/a^2 - (y-k)^2/b^2 = 1.\]
02
Find the Center
The center of the hyperbola is the midpoint of the line segment joining the vertices. The midpoint formula \(\left( \frac{x_1+x_2}{2}, \frac{y_1+y_2}{2} \right)\) gives us:\[ h = \frac{6+0}{2} = 3, \, k = \frac{-6+-6}{2} = -6.\]Thus, the center is \((3, -6)\).
03
Calculate \(a^2\)
The distance between the vertices is equal to \(2a\). The distance between the vertices \((6, -6)\) and \((0, -6)\) is \(6 - 0 = 6.\) Thus, \(2a = 6,\) so \(a = 3,\) and therefore, \(a^2 = 9.\)
04
Calculate \(c^2\) Using the Foci
The distance from the center to each focus is \(c\). The foci are given as \((3 \pm \sqrt{13}, -6)\), so \(c = \sqrt{13}\) and \(c^2 = 13.\)
05
Find \(b^2\) Using \(a^2\) and \(c^2\)
For a hyperbola, the relationship \(c^2 = a^2 + b^2\) must hold. Substituting the known values, we get:\[ c^2 = a^2 + b^2.\]\[ 13 = 9 + b^2.\]Solving for \(b^2\), we find \[ b^2 = 4.\]
06
Write the Equation of the Hyperbola
Substitute \(h\), \(k\), \(a^2\), and \(b^2\) into the standard hyperbola equation:\[ \frac{(x-3)^2}{9} - \frac{(y+6)^2}{4} = 1.\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertices of a Hyperbola
In a hyperbola, the vertices are key points where each branch of the hyperbola is closest to its center. They define how "wide" a hyperbola opens along its axis. Given vertices \(6,-6\) and \(0,-6\), it's clear that they lie horizontally. This indicates the hyperbola opens horizontally, which means the standard form of the equation is typically: \[\frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1.\]
- The vertices are equally spaced from the center in opposite directions along the transverse axis.
- The distance between the vertices, which is \(2a\), helps determine the "stretch" of the hyperbola along the transverse axis.
- In this problem, since the distance between the vertices is \(6\), we find that \(a = 3\).
Foci of a Hyperbola
Every hyperbola has two foci (plural of focus), which are points used to define the hyperbola's shape and properties. Foci of a hyperbola are always located along the major axis. For this specific hyperbola, the foci are \(3 \pm \sqrt{13}, -6\).
- The distance from the center to each focus is denoted as \(c\).
- Using the given foci, it's determined that \(c = \sqrt{13}\).
- For hyperbolas, the relationship is \(c^2 = a^2 + b^2\).
Center of a Hyperbola
The center of a hyperbola is the midpoint between its two vertices. This point serves as a reference for the symmetry of the hyperbola. The center provides a pivot point around which the branches curve away. Given vertices \(6,-6\) and \(0,-6\), the center can be calculated using the midpoint formula:
- Since the center lies on both the transverse and conjugate axes, it's crucial for locating the hyperbola in the coordinate plane.
- The coordinates of the center are used directly in the equation of the hyperbola as \(h\) and \(k\).
- In our equation, they affect how we shift the standard form along both the x and y axes.