Chapter 10: Problem 19
Show that the graph of the given equation consists either of a single point or of no points. $$x^{2}+y^{2}-6 x-10 y+84=0$$
Short Answer
Expert verified
There are no points on the graph because the radius squared is negative.
Step by step solution
01
Recognize the Equation Type
The given equation is a quadratic equation in terms of both \(x\) and \(y\). Specifically, it resembles the general form of a circle equation \(x^2 + y^2 + Dx + Ey + F = 0\). We need to determine if this represents an actual circle, a single point, or no points.
02
Rewrite in Standard Circle Form
To convert the equation into the standard form \((x-h)^2 + (y-k)^2 = r^2\), we complete the square for both \(x\) and \(y\). Start with \(x^2 - 6x\) and complete the square by adding and subtracting \(9\):\[(x^2 - 6x + 9) - 9\].For \(y^2 - 10y\), complete the square by adding and subtracting \(25\):\[(y^2 - 10y + 25) - 25\].Thus, the equation becomes:\[(x-3)^2 - 9 + (y-5)^2 - 25 + 84 = 0\].
03
Simplify the Equation
Combine the constants:\[(x-3)^2 + (y-5)^2 + 50 = 0\].Rearrange the equation to:\[(x-3)^2 + (y-5)^2 = -50\].
04
Analyze the Result
The equation \((x-3)^2 + (y-5)^2 = -50\) represents the equation of a circle centered at \((3, 5)\) with a radius \(r\) where \(r^2 = -50\). Since the square of a radius cannot be negative, no real points satisfy this equation.
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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 form that reveals key features of the equation. It helps convert a quadratic expression like \[ x^2 + bx \]into a perfect square trinomial:\[ (x-h)^2 \].
This transformation is essential when solving problems involving circle equations, as it helps us discern the center and radius of a circle. To complete the square for a term like \( x^2 - 6x \), we:
This transformation is essential when solving problems involving circle equations, as it helps us discern the center and radius of a circle. To complete the square for a term like \( x^2 - 6x \), we:
- Take half of the coefficient of \( x\), which is \(-6\), and divide it by 2 to get \(-3\).
- Square \(-3\) to get \(9\).
- Add and subtract \(9\) in the equation to form \((x-3)^2\).
- Half of \(-10\) is \(-5\); squaring it gives \(25\).
- Add and subtract \(25 \) to complete the square for \( y\).
- This process turns the expression into \((y-5)^2\).
The aim is to find a cleaner form, making analysis of the geometric properties easier.
Circle Equation
The concept of a circle's equation often appears in algebra and geometry. The standard form of a circle's equation is:\[(x-h)^2 + (y-k)^2 = r^2\]where \((h, k)\) defines the circle's center, and \(r\) is the radius.
When completing the square, the purpose is to transform a quadratic equation into this circle equation pattern. A typical quadratic manifestation of a circle equation includes terms like \(x^2\), \(y^2\), \(x\), and \(y\).
In the example given, the conversion to the circle equation sought to identify it. Sadly, after simplifying, we realized:\[(x-3)^2 + (y-5)^2 = -50\]which indicates an impossible situation — a circle with a negative radius squared \(r^2\). This implies there are no solutions on the Cartesian plane, as the radius of a real circle can never be negative.
This analysis helps us understand the geometric interpretation of the equation, but it may also identify cases where what looks like a circle does not exist in the real world.
When completing the square, the purpose is to transform a quadratic equation into this circle equation pattern. A typical quadratic manifestation of a circle equation includes terms like \(x^2\), \(y^2\), \(x\), and \(y\).
In the example given, the conversion to the circle equation sought to identify it. Sadly, after simplifying, we realized:\[(x-3)^2 + (y-5)^2 = -50\]which indicates an impossible situation — a circle with a negative radius squared \(r^2\). This implies there are no solutions on the Cartesian plane, as the radius of a real circle can never be negative.
This analysis helps us understand the geometric interpretation of the equation, but it may also identify cases where what looks like a circle does not exist in the real world.
Graph Analysis
Graph analysis involves interpreting equations in geometric terms, particularly on the Cartesian plane. By analyzing the resulting expression,\[(x-3)^2 + (y-5)^2 = -50\],we determined if graphing is possible.
The terms \((x-3)^2\) and \((y-5)^2\) suggest a circle around the point \((3, 5)\). However, a critical observation here is that the right side, \(-50\), cannot correspond to a valid radius squared since squares are always non-negative.
Thus, by graph analysis, we conclude this equation models no point in reality. In visual terms:
The terms \((x-3)^2\) and \((y-5)^2\) suggest a circle around the point \((3, 5)\). However, a critical observation here is that the right side, \(-50\), cannot correspond to a valid radius squared since squares are always non-negative.
Thus, by graph analysis, we conclude this equation models no point in reality. In visual terms:
- A graph with no valid points means it's empty.
- There are no intersection points between the plane and the given equation.