Chapter 10: Problem 28
Find the coordinates of the vertices and foci and the equations of the asymptotes for the hyperbola with the given equation. Then graph the hyperbola. $$ y^{2}-3 x^{2}+6 y+6 x-18=0 $$
Short Answer
Expert verified
Center: (1, -3); vertices: (1, -3±2√6); foci: (1, -3±4√2); asymptotes: y+3=±√3(x-1).
Step by step solution
01
Rewrite in Standard Form
Start by rewriting the given equation in the standard form of a hyperbola. The equation is \( y^2 - 3x^2 + 6y + 6x - 18 = 0 \). Begin by rearranging terms and grouping the \( y \) and \( x \) terms:\[y^2 + 6y - 3(x^2 - 2x) = 18\]Next, complete the square for both the \( y \) and \( x \) terms.
02
Complete the Square for y
To complete the square for \( y^2 + 6y \):1. Take half of the coefficient of \( y \) (which is 6), square it: \( (\frac{6}{2})^2 = 9 \).2. Add and subtract this square inside the equation:\[(y^2 + 6y + 9) - 9 - 3(x^2 - 2x) = 18\]This simplifies to:\[(y + 3)^2 - 9 - 3(x^2 - 2x) = 18\]
03
Complete the Square for x
For the \( -3(x^2 - 2x) \) term, complete the square:1. Factor out \(-3\) and complete the square inside: \( -3[(x^2 - 2x + 1) - 1] \).2. This becomes \( -3((x-1)^2 - 1) = -3(x-1)^2 + 3 \).Now, rewrite the equation including these squares:\[(y + 3)^2 - 9 - 3(x-1)^2 + 3 = 18\]
04
Simplify and Write the Equation in Standard Form
Simplify the equation from Step 3:\[(y + 3)^2 - 3(x-1)^2 - 6 = 18\]Add 6 to both sides:\[(y + 3)^2 - 3(x-1)^2 = 24\]Divide the entire equation by 24 to get:\[\frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1\]This is the standard form of a hyperbola with its transverse axis vertical.
05
Identify the Vertices and Foci
From the standard form \( \frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1 \):- The center is \((h, k) = (1, -3)\).- \( a^2 = 24 \) (so \( a = \sqrt{24} = 2\sqrt{6} \)).- \( b^2 = 8 \) (so \( b = \sqrt{8} = 2\sqrt{2} \)).- To find \( c \) use \( c^2 = a^2 + b^2 = 24 + 8 = 32 \) \( c = \sqrt{32} = 4\sqrt{2} \).Thus, the vertices are at \((1, -3 \pm 2\sqrt{6})\) and the foci are at \((1, -3 \pm 4\sqrt{2})\).
06
Determine the Asymptotes
For a hyperbola with a vertical transverse axis, the equations of the asymptotes are:\[(y + 3) = \pm \frac{a}{b}(x - 1)\]Substitute \( a = 2\sqrt{6} \) and \( b = 2\sqrt{2} \):\[(y + 3) = \pm \frac{2\sqrt{6}}{2\sqrt{2}} (x - 1)\]This simplifies to:\[(y + 3) = \pm \sqrt{3}(x - 1)\]Therefore, the equations of the asymptotes are \( y + 3 = \sqrt{3}(x - 1) \) and \( y + 3 = -\sqrt{3}(x - 1) \).
07
Graph the Hyperbola
Using the center \((1, -3)\), draw the vertices along the transverse axis (vertical) at \((1, -3 \pm 2\sqrt{6})\). Plot the foci at \((1, -3 \pm 4\sqrt{2})\). Draw the asymptotes lines using their equations. The hyperbola opens upward and downward along the y-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertices
When dealing with a hyperbola, the vertices are key points that define the shape and structure of the curve. They are the points where the hyperbola intersects its transverse axis.. For the equation \( \frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1 \), the center of the hyperbola is located at \((1, -3)\).. Since the transverse axis is vertical, the vertices lie directly above and below this center point. To find them, you calculate using \( a = \sqrt{24} = 2\sqrt{6} \):
- Add \( 2\sqrt{6} \) to the y-coordinate: \( -3 + 2\sqrt{6} \).
- Subtract \( 2\sqrt{6} \) from the y-coordinate: \( -3 - 2\sqrt{6} \).
Foci
The foci of a hyperbola play a crucial role in its geometric properties. They influence the shape of the hyperbola and are used in its definition.. In the equation \( \frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1 \), the foci are positioned along the same axis as the vertices but further out.. To determine the location of the foci, we calculate the distance \( c \) using the relationship \( c^2 = a^2 + b^2 \):
- Compute \( c = \sqrt{32} = 4\sqrt{2} \).
- Add \( 4\sqrt{2} \) to the y-coordinate of the center: \( -3 + 4\sqrt{2} \).
- Subtract \( 4\sqrt{2} \) from the y-coordinate of the center: \( -3 - 4\sqrt{2} \).
Asymptotes
Asymptotes are lines that the hyperbola approaches but never intersects. They help define the overall shape and orientation of the hyperbola.. For a hyperbola with the equation \( \frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1 \), we have vertical asymptotes since the transverse axis is vertical.. The equations of the asymptotes are found using the formula \[ (y + 3) = \pm \frac{a}{b}(x - 1) \] Substituting \( a = 2\sqrt{6} \) and \( b = 2\sqrt{2} \) gives:
- \( (y + 3) = \sqrt{3}(x - 1) \)
- \( (y + 3) = -\sqrt{3}(x - 1) \)
Graphing Hyperbolas
Graphing a hyperbola involves several steps but offers a clear visualization of its properties. Starting with the equation \( \frac{(y + 3)^2}{24} - \frac{(x - 1)^2}{8} = 1 \), we can graph by following these points:.. Identify the center, found at \((1, -3)\). This center acts as a reference point for other important features of the hyperbola.
Proceed to plot the vertices, which provide crucial points along the transverse axis: \((1, -3 + 2\sqrt{6})\) and \((1, -3 - 2\sqrt{6})\).
Next, mark the foci at \((1, -3 + 4\sqrt{2})\) and \((1, -3 - 4\sqrt{2})\).. These focus points help in shaping the curve and validating its paths.
Finally, draw the asymptotes from the equations:\( y + 3 = \pm \sqrt{3}(x - 1) \).. These diagonal lines serve as the guides, showing the tendency of the hyperbola as it extends outward.
Proceed to plot the vertices, which provide crucial points along the transverse axis: \((1, -3 + 2\sqrt{6})\) and \((1, -3 - 2\sqrt{6})\).
Next, mark the foci at \((1, -3 + 4\sqrt{2})\) and \((1, -3 - 4\sqrt{2})\).. These focus points help in shaping the curve and validating its paths.
Finally, draw the asymptotes from the equations:\( y + 3 = \pm \sqrt{3}(x - 1) \).. These diagonal lines serve as the guides, showing the tendency of the hyperbola as it extends outward.
- Make sure the branches of the hyperbola approach, but never touch, these asymptotes.
- The hyperbola will open upwards and downwards from the center, forming two separate curves as the branches.