Chapter 9: Problem 26
Graph the nonlinear inequality. $$25 x^{2}-36 y^{2}+200 x+144 y-644 \geq 0$$
Short Answer
Expert verified
The inequality describes a hyperbola centered at (-4, 2). Graph it with vertices at (-10, 2) and (2, 2), and follow the direction along the x-axis.
Step by step solution
01
Rewrite the Inequality
The given inequality is \( 25x^2 - 36y^2 + 200x + 144y - 644 \geq 0 \). Begin by moving the constant term to the other side of the inequality to isolate the quadratic terms: \( 25x^2 - 36y^2 + 200x + 144y \geq 644 \).
02
Complete the Square for x-Terms
Focus on the x-terms: \( 25x^2 + 200x \). Factor out the coefficient of \( x^2 \), which is 25: \( 25(x^2 + 8x) \). To complete the square, take half of the coefficient of \( x \) (which is 8), square it (\( 4^2 = 16 \)), and add and subtract it inside the parenthesis: \( 25(x^2 + 8x + 16 - 16) \), simplifying to \( 25((x + 4)^2 - 16) \).
03
Complete the Square for y-Terms
Now complete the square for the y-terms: \( -36y^2 + 144y \). Factor out the coefficient of \( y^2 \), which is -36: \( -36(y^2 - 4y) \). To complete the square, take half of \( -4 \), square it (\( (-2)^2 = 4 \)), and add and subtract inside the parenthesis: \( -36(y^2 - 4y + 4 - 4) \), simplifying to \( -36((y - 2)^2 - 4) \).
04
Simplify the Expression
Substitute back the completed squares for x and y terms into the inequality: \( 25((x+4)^2 - 16) - 36((y-2)^2 - 4) \geq 644 \). Simplify this: \( 25(x+4)^2 - 400 - 36(y-2)^2 + 144 \geq 644 \). Combine constants: \( 25(x+4)^2 - 36(y-2)^2 \geq 900 \).
05
Divide by 900 to Standardize
To transform this into the standard form of an ellipse, divide every term by 900: \[ \frac{25(x+4)^2}{900} - \frac{36(y-2)^2}{900} \geq 1 \]. Simplify: \[ \frac{(x+4)^2}{36} - \frac{(y-2)^2}{25} \geq 1 \]. This expression now represents a hyperbola.
06
Graph the Hyperbola
The standard form \[ \frac{(x+4)^2}{36} - \frac{(y-2)^2}{25} = 1 \] describes a hyperbola centered at (-4, 2) with vertices stretched along the x-axis. Using this form, sketch the hyperbola by plotting the center at (-4, 2), right and left vertices at (-4±6, 2), and asymptotes determined by the slope given by the ratios from the denominators.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
When tackling nonlinear inequalities, completing the square is a vital method. This technique centers around converting a quadratic expression, like ax² + bx, into a perfect square trinomial. Here's how it works in our case:
- For the x-terms: consider 25x² + 200x.
- Factor out the 25: 25(x² + 8x).
- To complete the square, take half of 8 (from x² + 8x), square it (4² = 16), and incorporate it: 25(x² + 8x + 16 - 16).
- This simplifies to 25((x + 4)² - 16) as x-terms.
Graphing Hyperbolas
When graphing hyperbolas, understanding their fundamental structure is essential. A hyperbola comprises two mirrored curves diverging from a center point, unlike an ellipse or a circle.
- In our problem, the key form \( \rac{(x+4)^2}{36} - \rac{(y-2)^2}{25} = 1 \) identifies a hyperbola with its center at (-4, 2).
- Hyperbolas stretch along axes dictated by denominators: here, widest along the x-axis.
- Sketch begins by plotting center and vertices, then drawing asymptotes which guide the hyperbola's shape.
Standard Form of a Hyperbola
The standard form of a hyperbola encapsulates all necessary information to graph it. For a hyperbola, this form follows \( \rac{(x-h)^2}{a^2} - \rac{(y-k)^2}{b^2} = 1 \).
- (h, k) represents the center, determined from completed square shifts, in our case (-4, 2).
- a² and b² derive from denominators sharing size and direction of the hyperbola.
- Given equation shows horizontal stretching: a hyperbola's nature arises when x² term precedes y².
Inequality Transformation
Transforming complex inequalities into simpler forms is crucial for solving and graphing them. The general task is to isolate terms to reformat inequalities.
- The original inequality was reshuffled, grouping x and y parts.
- Post completing square procedures, you simplify and standardize forms.
- Division by a constant consolidates it, making an inequality recognizable as a hyperbola.