Chapter 2: Problem 50
Exer. \(47-56:\) Find the center and radius of the circle with the given equation. $$x^{2}+y^{2}-10 x+18=0$$
Short Answer
Expert verified
Center: (5, 0); Radius: \( \sqrt{7} \)
Step by step solution
01
Move constant to the other side
Start by rewriting the equation to separate constants from the variables. The given equation is:\[ x^2 + y^2 - 10x + 18 = 0 \]Move the constant term to the right side:\[ x^2 + y^2 - 10x = -18 \]
02
Complete the square for the x terms
To complete the square for the x terms, we focus on the terms involving x:\[ x^2 - 10x \]Take half of the coefficient of x, which is -10, to get -5, and square it, which gives 25. Add and subtract 25 inside the equation:\[ (x^2 - 10x + 25) - 25 + y^2 = -18 \]
03
Form a perfect square trinomial
Rewrite the expression containing x as a perfect square trinomial:\[ (x - 5)^2 - 25 + y^2 = -18 \]
04
Move new constant terms to the other side
Add 25 to both sides to balance the equation:\[ (x - 5)^2 + y^2 = 7 \]
05
Identify the center and radius
The standard form of a circle's equation is \( (x - h)^2 + (y - k)^2 = r^2 \), where (h, k) is the center and r is the radius.By comparing, we see that:- Center (h, k) is (5, 0)- Radius r is \( \sqrt{7} \)
06
Final Verification
Make sure the derived equation \( (x - 5)^2 + y^2 = 7 \) is consistent with a circle in the standard form, confirming the calculations for center and radius.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
Completing the square is a method used in algebra to convert a quadratic expression into a perfect square trinomial. This process is vital for solving quadratic equations and finding the standard form of a circle equation. In the given problem, we start with an equation:
\[x^2 + y^2 - 10x + 18 = 0\]
Our goal is to complete the square for the terms involving \(x\). Follow these simple steps:
\[(x^2 - 10x + 25) - 25 + y^2 = -18\]
This method rearranges the quadratic equation into a more workable form, where one part is a perfect square trinomial.
\[x^2 + y^2 - 10x + 18 = 0\]
Our goal is to complete the square for the terms involving \(x\). Follow these simple steps:
- Focus on the \(x\) terms: \(x^2 - 10x\).
- Take half of the coefficient of \(x\) (here, \(-10\)), resulting in \(-5\), and then square it. You get 25.
- Add and subtract this squared value (25) to the expression.
\[(x^2 - 10x + 25) - 25 + y^2 = -18\]
This method rearranges the quadratic equation into a more workable form, where one part is a perfect square trinomial.
Standard Form of a Circle
The standard form of a circle is essential in mathematics to easily identify the circle's properties, like its center and radius. This format is:
\[(x - h)^2 + (y - k)^2 = r^2\]
Here, \((h, k)\) is the circle's center, and \(r\) is the radius. After completing the square in the problem, the equation is brought to:
\[(x - 5)^2 + y^2 = 7\]
In this structure, it's easy to spot the values that describe the circle's key characteristics:
\[(x - h)^2 + (y - k)^2 = r^2\]
Here, \((h, k)\) is the circle's center, and \(r\) is the radius. After completing the square in the problem, the equation is brought to:
\[(x - 5)^2 + y^2 = 7\]
In this structure, it's easy to spot the values that describe the circle's key characteristics:
- Like terms from the original equation become recognized parts of a geometric shape.
- Position (shift of the graph) is clear by the terms \((x-5)\).
Center and Radius of a Circle
By understanding the standard form conversion, we can now extract the center and radius from the circle equation. From:
\[(x - 5)^2 + y^2 = 7\]
We can directly see:
\[(x - 5)^2 + y^2 = 7\]
We can directly see:
- The center of the circle, represented by \((h, k)\), is found at \((5, 0)\).
- The radius \(r\) is the square root of the right-hand side constant, \(\sqrt{7}\).
- The center is the middle point around which the circle is perfectly balanced.
- The radius determines how far the boundary is from the center in all directions.