Chapter 0: Problem 19
Find the center and radius of the circle with the given equation. $$ x^{2}+y^{2}-12 x+35=0 $$
Short Answer
Expert verified
Center: (6, 0); Radius: 1.
Step by step solution
01
Rearrange the Equation
Start by rearranging the given circle equation, \( x^2 + y^2 - 12x + 35 = 0 \), to group the \( x \) terms together with \( x^2 \), and separate out the \( y^2 \) term: \( x^2 - 12x + y^2 = -35 \).
02
Complete the Square for x
To complete the square for the \( x \) terms, take half of the coefficient of \( x \), which is \(-12\). Half of \(-12\) is \(-6\). Then square \(-6\) to get \(36\). Add \(36\) to both sides of the equation to balance it, resulting in \( x^2 - 12x + 36 + y^2 = -35 + 36 \). This simplifies to \((x-6)^2 + y^2 = 1\).
03
Identify the Center and Radius
Now that the equation is in the form \((x-h)^2 + (y-k)^2 = r^2\), identify the center \((h, k)\) and radius \(r\). The expression \((x-6)^2 + y^2 = 1\) indicates that \(h = 6\), \(k = 0\), and \(r^2 = 1\). Thus, the center of the circle is \((6, 0)\) and the radius is \(r = \sqrt{1} = 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
When dealing with the equation of a circle, often times it is not given in its standard form. To transform a quadratic equation into a recognizable circle equation, one of the most effective techniques used is **completing the square**.
This method helps to rewrite the equation into a perfect square form, making it easier to identify properties of the circle such as the center and the radius.
Here's a quick step-by-step guide:
This method helps to rewrite the equation into a perfect square form, making it easier to identify properties of the circle such as the center and the radius.
Here's a quick step-by-step guide:
- Look at the terms involving the variable, such as the quadratic and linear terms. For a monomial like \( x^2 - 12x \), you'll focus on the \( x \)-related terms.
- Take half of the linear coefficient (in this case, for \(-12x\) it is \(-6\)), and then square it to make a complete square, which gives you \(36\).
- Add and subtract the squared term in the equation to balance it. This ensures the equation remains equivalent while transforming it into a form that can be easily manipulated.
Circle Center
After completing the square, the equation of the circle generally appears as \((x-h)^2 + (y-k)^2 = r^2\). From this, the center of the circle \((h, k)\) is straightforward to identify.
The term \((x-h)^2\) indicates a shift of the circle's center \(h\) units along the x-axis, while the \(k\) in \((y-k)^2\) represents a vertical movement along the y-axis.
In our rearranged equation \((x-6)^2 + y^2 = 1\), you can discern:
The term \((x-h)^2\) indicates a shift of the circle's center \(h\) units along the x-axis, while the \(k\) in \((y-k)^2\) represents a vertical movement along the y-axis.
In our rearranged equation \((x-6)^2 + y^2 = 1\), you can discern:
- For the x-component, \(h=6\) showing a shift to the right.
- For the y-component, \(k=0\), meaning no vertical shift has occurred.
Circle Radius
Finally, moving on to calculating the **circle radius**, we use the transformed circle equation, \((x-h)^2 + (y-k)^2 = r^2\). Here, \(r^2\) is the squared value of the circle's radius.
The provided example simplifies to \((x-6)^2 + y^2 = 1\), with \(r^2 = 1\). Thus, the radius \(r\) is derived by taking the square root of \(r^2\).
The provided example simplifies to \((x-6)^2 + y^2 = 1\), with \(r^2 = 1\). Thus, the radius \(r\) is derived by taking the square root of \(r^2\).
- The calculation \(r = \sqrt{1} = 1\) tells us the radius is a single unit long.