Chapter 10: Problem 14
Write an equation for the hyperbola that satisfies each set of conditions. vertices \((9,-3)\) and \((-5,-3),\) foci \((2 \pm \sqrt{53},-3)\)
Short Answer
Expert verified
The equation is \( \frac{(x-2)^2}{49} - \frac{(y+3)^2}{4} = 1 \).
Step by step solution
01
Determine the center
The vertices of the hyperbola are (9,-3)and (-5,-3).The center is the midpoint of these two points. Calculate it using the midpoint formula:\[\left(\frac{9 + (-5)}{2}, \frac{-3 + (-3)}{2}\right) = \left(\frac{4}{2}, \frac{-6}{2}\right) = (2, -3)\]
02
Find the distance between the vertices
Using the distance formula, calculate the distance between the vertices (9, -3)and (-5, -3):\[\sqrt{(9 - (-5))^2 + ((-3) - (-3))^2} = \sqrt{14^2} = 14\] The distance between the vertices is 14, so the length of the transverse axis is 14. Since the formula for hyperbolas is 2a,we find a = \frac{14}{2} = 7.
03
Verify and assign the orientation
Since the y-coordinates of the centers are the same (both -3), this hyperbola is oriented horizontally. Hence, its general equation takes the form:\[\frac{(x - h)^2}{a^2} - \frac{(y - k)^2}{b^2} = 1\] where \ (h, k)\ = (2, -3).We already knowa = 7.\, so (a^2) = 49.
04
Calculate the value of 'c'
The foci are given as:(2 + \sqrt{53}, -3) \text{ and } (2 - \sqrt{53}, -3).\The distance from the center to a focus is\(c = \sqrt{53}.\) The relationship between a,\ b, \text{ and } c\ is a^2 + b^2 = c^2.\ Thus, we have:\[a^2 + b^2 = c^2gives \ 49 + b^2 = 53.\]
05
Solve for 'b^2'
Continuing from Step 4:\[49 + b^2 = 53 \b^2 = 53 - 49 = 4\]
06
Write the equation of the hyperbola
The general formula for the hyperbola here is:\[\frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1\]Knowing that h = 2, k = -3, a^2 = 49, b^2 = 4,plug these values in:\[\frac{(x-2)^2}{49} - \frac{(y+3)^2}{4} = 1\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertices
In hyperbolas, the vertices are key points from which we can gather a lot of information to construct the equation. For this exercise, we have the vertices at
- (9, -3)
- (-5, -3)
Foci
The foci of a hyperbola are also important. They lie on the transverse axis, just like the vertices, but are further from the center. In this hyperbola's case, the foci are given as:
- (2 + \(\sqrt{53}\), -3)
- (2 - \(\sqrt{53}\), -3)
Transverse Axis
The transverse axis is a critical line segment for hyperbolas. It extends between the vertices and through the center. In a hyperbola with horizontal orientation, like this example, it primarily lies along the x-axis. The length of the transverse axis aligns with the distance between the vertices.To find the transverse axis, we calculated the distance between the two vertices \((9, -3)\) and \((-5, -3)\), resulting in a distance of 14. This automatically tells us a key property: the full length of the transverse axis is 14. Since the transverse axis length is given by \(2a\), we find \(a = \frac{14}{2} = 7\). This length of 7 is used in calculations concerning hyperbola dimensions.
Center Calculation
Calculating the center of a hyperbola is straightforward when we have both vertices. The center is the midpoint of the line segment connecting the vertices. We apply the midpoint formula to find it. Given vertices
- (9, -3)
- (-5, -3)
Distance Formula
The distance formula helps measure the space between two points in a plane. It's an essential tool in determining various attributes of a hyperbola. In this exercise, the formula was vital for:
- Finding the distance between the vertices.
- Ensuring the accuracy of the transverse axis length.