Chapter 13: Problem 52
Sketch the graph of each equation. If the graph is a parabola, find irs vertex. If the graph is a circle, find its center and radius. $$x^{2}+y^{2}+6 x+10 y-2=0$$
Short Answer
Expert verified
Center: (-3, -5), Radius: 6.
Step by step solution
01
Identify the Equation Type
The given equation is \(x^2 + y^2 + 6x + 10y - 2 = 0\). It contains both \(x^2\) and \(y^2\) terms with equal coefficients, indicating that it's a circle.
02
Rearrange and Group Terms
To rearrange and group the quadratic terms, express the equation in a way that allows for completing the square:\[ x^2 + 6x + y^2 + 10y = 2 \]
03
Complete the Square for x-terms
For the \(x\)-terms, we have \(x^2 + 6x\). To complete the square, take half of the coefficient of \(x\) (which is 3), square it, and add and subtract it inside the expression: \(x^2 + 6x = (x+3)^2 - 9\).
04
Complete the Square for y-terms
For the \(y\)-terms, we have \(y^2 + 10y\). Take half of the coefficient of \(y\) (which is 5), square it, and add and subtract it:\(y^2 + 10y = (y+5)^2 - 25\).
05
Combine and Simplify the Equation
Substitute the completed squares back into the equation:\[(x + 3)^2 - 9 + (y + 5)^2 - 25 = 2 \]Combine and simplify:\[(x + 3)^2 + (y + 5)^2 = 36\]
06
Identify the Center and Radius
The equation \((x + 3)^2 + (y + 5)^2 = 36\) represents a circle with center at \((-3, -5)\) and radius \(\sqrt{36} = 6\).
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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 method used to transform a quadratic expression into a perfect square trinomial, making it easier to analyze or graph. The main idea is to restructure the quadratic terms in an equation so that they form a square binomial.
Here's how it works:
Here's how it works:
- Consider a generic quadratic expression in terms of one variable, such as \(x^2 + bx\).
- Take half of the coefficient of \(x\), which is \(\frac{b}{2}\), and square it to complete the square.
- Add and subtract this squared value in the expression to form a perfect square trinomial. This can be expressed as \((x + \frac{b}{2})^2 - (\frac{b}{2})^2\).
Circle Graphing
Graphing a circle involves plotting all the points in the plane that are equidistant from a central point, known as the center. The equation of a circle in standard form is \((x-h)^2 + (y-k)^2 = r^2\), where \((h, k)\) is the center and \(r\) is the radius.
To graph the circle from the transformed equation \((x + 3)^2 + (y + 5)^2 = 36\):
To graph the circle from the transformed equation \((x + 3)^2 + (y + 5)^2 = 36\):
- First, recognize that the circle's center is at \((-3, -5)\) because the equation is in the form \((x-h)^2 + (y-k)^2 = r^2\) and looks like \((x - (-3))^2 + (y - (-5))^2\).
- The radius is the square root of 36, which is 6.
- Once you have the center and radius, plot the center on the coordinate plane, and draw a circle around it with the specified radius.
Center and Radius
The center and radius of a circle provide a lot of information that makes graphing straightforward and provide insights into the geometry of the circle.
Let's break down why the center and radius are so crucial:
Understanding these aspects enables one to construct the circle accurately and appreciate its geometric properties.
Let's break down why the center and radius are so crucial:
- The center, given by \( (h, k) \), is a fixed point from which all points on the circle are equidistant.
- The radius, represented by \( r \), is that consistent distance from the center to any point on the circle. It's always positive as a measure of length.
Understanding these aspects enables one to construct the circle accurately and appreciate its geometric properties.