Chapter 12: Problem 42
Rewrite each equation in the standard form for the equation of a circle, and identify its center and radius. $$x^{2}-3 x+y^{2}=0$$
Short Answer
Expert verified
Center: (\frac{3}{2}, 0). Radius: \frac{3}{2}.
Step by step solution
01
Rewrite the equation and group terms
Start by rewriting the given equation and grouping the terms involving the same variable together:\[x^2 - 3x + y^2 = 0\]To complete the square, we'll isolate the terms involving \(x\) and \(y\) separately.
02
Complete the square for the \(x\)-terms
To complete the square for the \(x\)-terms, take half of the linear coefficient of \(x\), square it, and add and subtract this value inside the equation:\[x^2 - 3x\text{ }\to\text{ } x^2 - 3x + \frac{9}{4} - \frac{9}{4} \ = (x - \frac{3}{2})^2 - \frac{9}{4}\]
03
Combine the completed square with the original equation
Now, substitute the completed square back into the equation, combined with the original \(y^2\) term:\[(x - \frac{3}{2})^2 - \frac{9}{4} + y^2 = 0\]
04
Simplify and isolate the completed square term
Next, simplify and isolate the completed square term and the constant term by combining them on the same side of the equation:\[(x - \frac{3}{2})^2 + y^2 = \frac{9}{4}\]
05
Rewrite in standard form and identify center and radius
The equation \[(x - \frac{3}{2})^2 + y^2 = \frac{9}{4}\] is in standard form for a circle: \((x - h)^2 + (y - k)^2 = r^2\).Identify the center \( (h, k) \): \( (\frac{3}{2}, 0) \)Identify the radius \( r \): \( \frac{3}{2} \)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
completing the square
To understand completing the square, think of it as a method to transform a quadratic expression into a perfect square trinomial. This technique helps in rewriting the equation of a circle in standard form. Consider the quadratic expression from the given problem:
Let's take the term involving 'x', which is \( x^2 - 3x \).
To complete the square, follow these steps:
Let's take the term involving 'x', which is \( x^2 - 3x \).
To complete the square, follow these steps:
- Take half of the linear coefficient (the coefficient of x) which is -3. Half of -3 is -\(\frac{3}{2}\).
- Square this result: \(( -\frac{3}{2} )^2 = \frac{9}{4}\).
- Add and subtract this squared value inside the equation: \(x^2 - 3x + \frac{9}{4} - \frac{9}{4}\). This turns our expression into: \((x - \frac{3}{2})^2 - \frac{9}{4}\).
standard form
The standard form of the equation of a circle presents it in an easily recognizable format. The general standard form is: \[ (x - h)^2 + (y - k)^2 = r^2 \]
Here:
Here:
- \( (x - h) \) represents the horizontal component from the center of the circle.
- \( (y - k) \) represents the vertical component from the center of the circle.
- \( r \) is the radius of the circle.
- First, complete the square for the x-terms, resulting in \( (x - \frac{3}{2})^2 - \frac{9}{4} \).
- Next, substitute this completed square back into the equation along with \( y^2 \): \[ (x - \frac{3}{2})^2 - \frac{9}{4} + y^2 = 0 \]
- Combine and simplify the constants on one side: \[ (x - \frac{3}{2})^2 + y^2 = \frac{9}{4} \]
center and radius
The center and radius are key features of a circle. In standard form, the equation of a circle can be written as: \[ (x - h)^2 + (y - k)^2 = r^2 \]
From this equation:
From this equation:
- The center of the circle is at coordinates (h, k).
- The radius is \( r \).
- We can see that the center (h, k) is derived from the expression inside the parentheses: \(x - \frac{3}{2}\) and \(y \). Thus, the center is \( (\frac{3}{2}, 0) \).
- To find the radius, take the square root of the constant term on the right side of the equation: \( \frac{9}{4} \). The radius \( r \) is therefore \( \frac{3}{2} \).