Problem 8 - Calculus Early Transcendentals: Pearson New International Edition

Question

Name the conic corresponding to the given equation. \(x^{2}-4 y^{2}=4\)

Step-by-Step Solution

Answer

The conic is a hyperbola.

Step 1: Identify the terms

Examine the given equation \(x^{2} - 4y^{2} = 4\). The terms \(x^2\) and \(-4y^2\) indicate the square terms are quadratic and have different signs.

Step 2: Compare with standard form

The standard form for a conic section of a hyperbola is \(Ax^2 + By^2 = C\), where \(A\) and \(B\) have opposite signs. Our equation \(x^{2} - 4y^{2} = 4\) matches this pattern with \(A = 1\) and \(B = -4\), confirming opposite signs.

Step 3: Conclusion on the type of conic

Since the square terms \(x^2\) and \(-4y^2\) have opposite signs, the conic section is a hyperbola.

Key Concepts

Hyperbola

A hyperbola is a fascinating type of conic section. Created by the intersection of a double cone, it has a unique shape that resembles two open curves, known as branches. A hyperbola is defined mathematically where the difference of distances to two fixed points, called foci, remains constant. Hyperbolas have several important properties:

• Two parts or branches that open either horizontally or vertically.
• A center point that lies midway between the foci.
• Asymptotes that pass through the center and guide the shape of the hyperbola.
• Both branches approach these asymptotes but never actually touch them.

In our equation, \(x^2 - 4y^2 = 4\), the different signs on the square terms indicate the curve is a hyperbola. This specific form tells us the curve's branches open along the x-axis.

Quadratic Equations

Quadratic equations involve terms raised to the second power, which you see in forms like \(ax^2 + bx + c = 0\). In our problem, the equation \(x^2 - 4y^2 = 4\) features quadratic terms, recognizing them as expressions with a degree of two. A quadratic equation can include single-variable terms or a combination of different variables, each raised to a power of two, as seen in our example with both \(x^2\) and \(y^2\). These expressions can create various conic section shapes, such as circles, ellipses, parabolas, and hyperbolas, depending on the specific configuration of terms. Here, the equation creates a hyperbola because the quadratic terms \(x^2\) and \(-4y^2\) reveal different signs, forming the hyperbola's characteristic shape.

Standard Form of Hyperbola

The standard form of a hyperbola equation varies based on how it is oriented in the plane:

• Horizontally oriented: \(\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1\)
• Vertically oriented: \(\frac{y^2}{b^2} - \frac{x^2}{a^2} = 1\)

The signs and positions of \(x^2\) and \(y^2\) in the equation determine the hyperbola's orientation. In our exercise, \(x^2 - 4y^2 = 4\) follows the pattern \(Ax^2 + By^2 = C\) with \(A = 1\) and \(B = -4\). This alignment of terms reveals opposite signs, confirming it as a hyperbola. To convert it into the standard hyperbola form expressing this same shape, you'd divide through by 4: \(\frac{x^2}{4} - \frac{y^2}{1} = 1\).This conversion simplifies identifying its geometric features, such as vertices and foci.

Mathematical Problem Solving

Mathematical problem solving is a crucial skill that involves breaking down complex problems into manageable parts. To tackle equations involving conic sections like hyperbolas, a step-by-step approach is usually best.

1. Identify the components: Recognize and analyze the equation’s terms. Here, noticing the square terms \(x^2\) and \(-4y^2\) is key.
2. Classify the equation: Compare it with known conic section forms. Finding that \(x^2 - 4y^2\) fits the hyperbola's form helped us deduce the shape.
3. Simplify and transform: Convert or rework the equation into its standard form, such as converting \(x^2 - 4y^2 = 4\) to its equivalent hyperbola form \(\frac{x^2}{4} - \frac{y^2}{1} = 1\).
4. Draw conclusions: Use the simplified form to extract more insights, such as identifying axis orientations, lengths, and asymptotes.

By systematically addressing each part of the problem, you can identify the conic section involved and apply the necessary mathematical techniques to solve and understand the problem more completely.