Chapter 10: Problem 36
Prove: If \(B \neq 0,\) then the graph of \(x^{2}+B x y+F=0\) is a hyperbola if \(F \neq 0\) and two intersecting lines if \(F=0\)
Short Answer
Expert verified
The graph is a hyperbola if \(F \neq 0\) and two intersecting lines if \(F = 0\).
Step by step solution
01
Check the Equation Form
Write down the given equation: \(x^2 + Bxy + F = 0\). This equation appears to be a conic section represented by a general quadratic equation of the form \(Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0\) where \(A = 1\), \(C = 0\), \(D = 0\), \(E = 0\), and we have the \(B\) coefficient affecting the \(xy\) term.
02
Evaluate the Discriminant
For conic sections, the discriminant \(\Delta = B^2 - 4AC\) determines the type of the curve. Plug in the values: \(\Delta = B^2 - 4 \times 1 \times 0 = B^2\). Since \(B eq 0\), \(\Delta = B^2 > 0\). When the discriminant is greater than zero, the conic section is a hyperbola.
03
Analyze the Case \(F = 0\)
For \(F = 0\), the equation reduces to \(x^2 + Bxy = 0\). Factorize this equation: \(x(x + By) = 0\). The solutions are \(x = 0\) or \(x + By = 0\), which represent two intersecting lines through the origin.
04
Analyze the Case \(F \neq 0\)
With \(F eq 0\), the equation \(x^2 + Bxy + F = 0\) cannot be factorized into linear factors, reaffirming that it represents a hyperbola as previously found from the discriminant being positive.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Hyperbola
A hyperbola is a type of conic section that looks like two mirrored curves. It can be thought of as a set of points where the difference in distances between each point and two fixed points, called foci, is constant.
In terms of algebra, a hyperbola is recognized by its general equation form:
In terms of algebra, a hyperbola is recognized by its general equation form:
- When you see a quadratic equation like \(Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0\), the type of conic section can be identified using the discriminant.
- The discriminant \(\Delta = B^2 - 4AC\) helps in identifying the specific conic: when \(\Delta > 0\), it indicates a hyperbola.
- In our exercise equation, \(x^2 + Bxy + F = 0\), the discriminant simplifies to \(B^2\), as \(C = 0\), leading to \(\Delta = B^2\).
Discriminant
The discriminant is a crucial determinant in classifying conic sections. It provides insight into the geometric nature of the equation represented.
When dealing with a quadratic equation of the form \(Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0\), the discriminant is calculated as \(\Delta = B^2 - 4AC\). Here's how it works:
When dealing with a quadratic equation of the form \(Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0\), the discriminant is calculated as \(\Delta = B^2 - 4AC\). Here's how it works:
- If \(\Delta > 0\), the equation represents a hyperbola.
- If \(\Delta = 0\), it indicates a parabola.
- If \(\Delta < 0\), it corresponds to an ellipse or a circle.
Intersecting Lines
Intersecting lines are formed when the equation can break down into two linear factors. This happens when the constant term allows perfect factorization.
Consider the equation \(x^2 + Bxy + F = 0\). Let's explore the condition for intersecting lines:
Intersecting at the point, usually the origin, gives a visual representation as simple straight lines crossing each other on a graph.
Consider the equation \(x^2 + Bxy + F = 0\). Let's explore the condition for intersecting lines:
- When \(F = 0\), the equation simplifies to \(x^2 + Bxy = 0\). This can be factorized as \(x(x + By) = 0\).
- Solving each factor gives the lines \(x = 0\) and \(x + By = 0\), which are two intersecting lines passing through the origin.
Intersecting at the point, usually the origin, gives a visual representation as simple straight lines crossing each other on a graph.