Chapter 12: Problem 31
\(29-32\) . (a) Use the discriminant to identify the conic. (b) Confirm your answer by graphing the conic using a graphing device. $$ 6 x^{2}+10 x y+3 y^{2}-6 y=36 $$
Short Answer
Expert verified
The conic is a hyperbola, confirmed by the discriminant and graphing.
Step by step solution
01
Write the General Form of the Conic
The given equation is:\[6x^2 + 10xy + 3y^2 - 6y = 36\]In the general quadratic form of a conic, which is \(Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0\), the coefficients for this equation are \(A = 6\), \(B = 10\), \(C = 3\), \(D = 0\), \(E = -6\), and \(F = -36\).
02
Calculate the Discriminant
The discriminant for a conic equation is given by \(B^2 - 4AC\). Substitute the values of \(B\), \(A\), and \(C\):\[B^2 - 4AC = 10^2 - 4(6)(3)\]\[= 100 - 72 = 28\]
03
Analyze the Discriminant
Use the discriminant to determine the type of conic:- If the discriminant is greater than 0, the conic is a hyperbola.- If the discriminant equals 0, the conic is a parabola.- If the discriminant is less than 0, the conic is an ellipse or circle.Since \(28 > 0\), the conic is a hyperbola.
04
Confirm by Graphing the Conic
Graph the conic equation \(6x^2 + 10xy + 3y^2 - 6y = 36\) using a graphing device. Observe if the graph resembles the shape characteristic of a hyperbola, which has two distinct branches opening either opposite or adjacent to each other.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Discriminant in Conic Sections
The discriminant is a useful tool in the study of conic sections. It's a number calculated from the coefficients of a quadratic equation. In this context, the equation is given as \( Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 \). The formula for the discriminant, \( B^2 - 4AC \), helps in identifying the type of conic section represented by the equation.
Here's how you can interpret the discriminant:
Here's how you can interpret the discriminant:
- If \( B^2 - 4AC > 0 \), the conic is a hyperbola.
- If \( B^2 - 4AC = 0 \), the conic is a parabola.
- If \( B^2 - 4AC < 0 \), the conic is an ellipse or could be a circle if it meets further conditions.
Recognizing a Hyperbola
A hyperbola is one of the fascinating conic sections and is recognized by its unique shape. It consists of two separate curves, called branches, that open in opposite directions.
When identifying a hyperbola from a quadratic equation, one indicator is the value of the discriminant explained earlier. If \( B^2 - 4AC > 0 \), it confirms the presence of a hyperbola.
When identifying a hyperbola from a quadratic equation, one indicator is the value of the discriminant explained earlier. If \( B^2 - 4AC > 0 \), it confirms the presence of a hyperbola.
- The branches can open horizontally or vertically, depending on the equation's structure.
- In the standard form, a hyperbola often has the term \( xy \) present, which affects its rotation and orientation on a graph.
Basics of Quadratic Equations in Conics
Quadratic equations are foundational to conic sections, encompassing different forms like circles, ellipses, parabolas, and hyperbolas. The general quadratic equation for a conic section is \( Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 \). This equation can represent various shapes depending on the values of \( A \), \( B \), and \( C \).
- When \( B = 0 \) and \( A eq C\), the equation represents either an ellipse or a hyperbola, depending on other conditions.
- A perfect square in \( y \) or \( x \) may hint at a parabola.
- If \( A = C \) and \( B = 0 \), the conic is a circle.
Graphing Conics to Confirm Their Nature
Graphing conic sections provides a visual confirmation of their nature, as it allows you to see the actual shape. Once you suspect a conic type via the discriminant, graphing checks if the shape corresponds to your conclusion.
To graph the conic equation \( 6x^2 + 10xy + 3y^2 - 6y = 36 \), a graphing tool or graphing calculator can be used. Upon graphing, examine these features:
To graph the conic equation \( 6x^2 + 10xy + 3y^2 - 6y = 36 \), a graphing tool or graphing calculator can be used. Upon graphing, examine these features:
- For a hyperbola, observe if there are two branches that mirror each other and open in opposite directions.
- Ensure the asymptotic lines, which guide the direction of the hyperbola's branches, are clear.
- If the graph does not display as expected, recheck the calculation inputs or settings.