Chapter 10: Problem 111
For the following exercises, sketch a graph of the hyperbola, labeling vertices and foci. $$-100 x^{2}+1000 x+y^{2}-10 y-2575=0$$
Short Answer
Expert verified
The hyperbola has vertices at (5, -5) and (5, 15), and foci at (5, 5±√101).
Step by step solution
01
Rearrange the Equation
We start by rearranging the given equation \(-100x^2 + 1000x + y^2 - 10y - 2575 = 0\). We can group like terms and move constants to the right. \[-100(x^2 - 10x) + (y^2 - 10y) = 2575\]
02
Complete the Square for x
Complete the square for the \(x\) terms. - Factor out the negative coefficient from the \(x\) terms: \[-100(x^2 - 10x)\] - To complete the square, take half of \(-10\) (which is \(-5\)) and square it to get \(25\), adjust the equation accordingly: \[-100((x^2 - 10x + 25) - 25)\] - Simplifying gives us: \[-100((x-5)^2) + 2500\]
03
Complete the Square for y
Complete the square for the \(y\) terms. - Take half of \(-10\) (which is \(-5\)) and square it to get \(25\), adjust the equation accordingly: \[(y^2 - 10y + 25) - 25\] - Simplification leads to: \[((y-5)^2) - 25\]
04
Substitute Back and Simplify
Substitute the equations from steps 2 and 3 back into the original rearranged equation and simplify. \[-100((x-5)^2) + 2500 + ((y-5)^2) - 25 = 2575\] Combine the constants: \[-100((x-5)^2) + (y-5)^2 = 100\]
05
Divide Through by Constant
Divide the entire equation by 100 to arrange in the standard form of a hyperbola: \[\frac{(y-5)^2}{100} - \frac{(x-5)^2}{1} = 1\] This is now in the form \(\frac{(y-k)^2}{a^2} - \frac{(x-h)^2}{b^2} = 1\), identifying it as a vertical hyperbola.
06
Determine and Label Vertices and Foci
For a vertical hyperbola, vertices are located \((h, k \pm a)\) and foci are located \((h, k \pm c)\) where \(c = \sqrt{a^2 + b^2}\). - Here, \(h=5\), \(k=5\), \(a=10\), \(b=1\), so: - Vertices: \((5, 5\pm 10)= (5, -5)\) and \((5, 15)\) - Foci: \(c = \sqrt{100 + 1} = \sqrt{101}\), giving foci as \((5, 5 \pm \sqrt{101})\)
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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 method used to transform a quadratic equation into a form that reveals important properties of the graph. This method is essential when dealing with conic sections like hyperbolas. To complete the square for a term such as \(x^2 + bx\), we want to rewrite it as \((x-h)^2\), where \(h\) is chosen such that the equation represents a perfect square trinomial.
For our equation, \(-100(x^2 - 10x)\), we begin by taking the coefficient of \(x\), which is \(-10\), and divide it by 2, resulting in \(-5\). Squaring \(-5\) gives us 25. We add and subtract this number inside the parentheses:
For our equation, \(-100(x^2 - 10x)\), we begin by taking the coefficient of \(x\), which is \(-10\), and divide it by 2, resulting in \(-5\). Squaring \(-5\) gives us 25. We add and subtract this number inside the parentheses:
- \[ -100(x^2 - 10x + 25 - 25) \]
- \[ -100((x - 5)^2 - 25) \]
- \((y^2 - 10y + 25 - 25)\)
- \[((y - 5)^2 - 25)\]
Equation of a Hyperbola
The equation of a hyperbola represents the algebraic relationship that describes its shape and orientation in the coordinate plane. In standard form, a hyperbola looks like \(\frac{(y-k)^2}{a^2} - \frac{(x-h)^2}{b^2} = 1\) for vertical hyperbolas, or \(\frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1\) for horizontal hyperbolas.
In our example, after completing the square and rearranging, we transform the initial equation into the form \[\frac{(y-5)^2}{100} - \frac{(x-5)^2}{1} = 1\]
In our example, after completing the square and rearranging, we transform the initial equation into the form \[\frac{(y-5)^2}{100} - \frac{(x-5)^2}{1} = 1\]
- Here, the minus sign between terms indicates a hyperbola.
- The positive term \((y-5)^2\) suggests the hyperbola is vertical.
- The expressions \((y-k)^2\) and \((x-h)^2\) show the translations along the axes.
- \((h, k) = (5, 5)\) sets the center of the hyperbola.
Vertices and Foci
Vertices and foci are critical elements in the anatomy of a hyperbola. They provide clues about the hyperbola's spread and exact position in the Cartesian plane.
For a vertical hyperbola like \(\frac{(y-5)^2}{100} - \frac{(x-5)^2}{1} = 1\), the formula for vertices is \((h, k \pm a)\), while the formula for the foci is \((h, k \pm c)\). The distance \(a\) represents half the length between the vertices along the axis of symmetry, and \(c\) is the distance from the center to each focus:
For a vertical hyperbola like \(\frac{(y-5)^2}{100} - \frac{(x-5)^2}{1} = 1\), the formula for vertices is \((h, k \pm a)\), while the formula for the foci is \((h, k \pm c)\). The distance \(a\) represents half the length between the vertices along the axis of symmetry, and \(c\) is the distance from the center to each focus:
- The vertices are found by identifying \(a\), where \(a = \sqrt{100} = 10\). So, the vertices are at \((5, 5 \pm 10) = (5, -5)\) and \((5, 15)\).
- The foci require computing \(c = \sqrt{a^2 + b^2} = \sqrt{101}\). Thus, the foci are \((5, 5 \pm \sqrt{101})\).
Standard Form of a Hyperbola
The standard form of a hyperbola is vital for graphing and understanding its geometrical properties and characteristics. Transforming an equation into this form involves completing the square and isolating terms.
For a vertical hyperbola such as our equation, we aim to express it as \(\frac{(y-k)^2}{a^2} - \frac{(x-h)^2}{b^2} = 1\). Once the equation is in this standard form, several attributes of the hyperbola are easily identifiable:
For a vertical hyperbola such as our equation, we aim to express it as \(\frac{(y-k)^2}{a^2} - \frac{(x-h)^2}{b^2} = 1\). Once the equation is in this standard form, several attributes of the hyperbola are easily identifiable:
- Signs indicate whether the hyperbola opens vertically or horizontally.
- \((h, k)\) represents the center of the hyperbola.
- \(a^2\) and \(b^2\) link to distances within the graph, \(a\) pertains to vertices and \(b\) relates to the conjugate axis.