Chapter 14: Problem 10
Determine the locus of the equation \(b^{2}-2 x^{2}=2 x y+y^{2}\) (Hint \(:\) Add \(x^{2}\) to both sides.)
Short Answer
Expert verified
Question: Find the locus of the equation \(b^2 - 2x^2 = 2xy + y^2\).
Answer: The locus of the given equation represents a hyperbola.
Step by step solution
01
Add \(x^2\) on both sides of the given equation
Add \(x^2\) to both sides of the equation: \((b^2 - 2x^2) + x^2 = (2xy + y^2) + x^2\)
Now the equation becomes:
\(b^2 - x^2 = x^2 + 2xy + y^2\)
02
Complete the square on the left and right sides
Observe that we can write the left and right sides of the equation as the difference and sum of squares, respectively:
\((b^2 - x^2) = (x^2 + 2xy + y^2)\)
Written in terms of squares:
\((b - x)(b + x) = (x + y)^2\)
03
Divide both sides by \((b+x)\)
Now, let's divide both sides of the equation by \((b + x)\):
\(\frac{(b - x)(b + x)}{b + x} = \frac{(x + y)^2}{b + x}\)
The \((b + x)\) terms cancel on the left side:
\(b - x = \frac{(x + y)^2}{b + x}\)
04
Express y in terms of x and b
Move the left side of the equation to the right side:
\(0 = \frac{(x + y)^2}{b + x} - (b - x)\)
Now, multiply both sides by \((b+x)\), which gives us:
\(0 = (x + y)^2 - (b - x)(b + x)\)
Now, we have:
\((b - x)(b + x) = (x + y)^2\)
Notice that on the left side, we have the difference of two squares again:
\((b^2 - x^2) = (x + y)^2\)
The locus of this equation is a combination of the properties of a hyperbola and a parabola. We can determine that this locus represents a hyperbola, as it corresponds to the difference of two squares, and retains some properties of a parabola with the equation \((x + y)^2\).
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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 mathematical technique used to rewrite quadratic equations in a way that reveals important features, like the vertex of a parabola or to solve equations involving conic sections. Let's break it down step by step.
- First, isolate terms involving the square, if necessary. In our example, we added \(x^2\) to both sides of the equation to reorganize it.
- Next, look at the terms you want to complete as a perfect square. For terms like \(x^2 + 2xy + y^2\), you can see these form the square of \((x+y)^2\).
- Write these terms as squared expressions, such as \((x+y)^2\) on one side and \((b - x)(b + x)\) on the other, which can also reveal structure.
Difference of Squares
The difference of squares is an algebraic expression that can be factored into the form \(a^2 - b^2 = (a - b)(a + b)\). This factoring reveals two things multiplied together.
- It's commonly used when dealing with expressions like \(b^2 - x^2\), which directly factors into \((b - x)(b + x)\).
- This factorization helps simplify the equation, making it easier to solve or interpret geometrically.
- Recognizing the difference of squares allows us to transition from seemingly complex expressions to simpler products.
Hyperbola Equation
A hyperbola is a type of conic section defined by its characteristic formula which often involves a difference of squares. The standard form of a rectangular hyperbola looks like \(\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1\).
- The equation given in the problem can be manipulated to show a hyperbolic structure, specifically by reorganizing and factorization.
- The recognition of the form \((b^2 - x^2) = (x + y)^2\) gives insight into its hyperbolic nature.
- Hyperbolas are significant because they represent loci of points satisfying a particular difference from the foci, which in terms of geometry, can model several scientific phenomena.