Chapter 6: Problem 30
\(16 x^{2}+16 y^{2}-64 x+32 y+55=0\)
Short Answer
Expert verified
The center of the circle is at (2,-1) and the radius is 1.25.
Step by step solution
01
Rewriting the equation
First rewrite the equation by gathering the \(x\) terms and \(y\) terms: \(16(x^2 - 4x) +16(y^2 + 2y) = -55\)
02
Completing the square
Complete the square for both \(x\) and \(y\) terms: \(16[(x-2)^2 - 4] +16[(y+1)^2 -1] = -55\). Which simplifies to \(16(x-2)^2 +16(y+1)^2 = -55 + 64 + 16 = 25\)
03
Determine the center and radius
Divide the entire equation by 16 to isolate the squared terms on one side, which gives us \((x-2)^2 +(y+1)^2 = 1.5625\). For equations of the form \((x-h)^2 + (y-k)^2 = r^2\), the center of the circle is at (h,k) and the radius is \(r\). Therefore the center of this circle is at (2,-1) and the radius is \(\sqrt{1.5625} = 1.25\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Equation of a Circle
The equation of a circle is a fundamental concept in geometry that describes the set of points which are equidistant from a given point, known as the center. In the standard form, this equation is represented as \[(x-h)^2 + (y-k)^2 = r^2\]Here,
- \( (h, k) \) represent the coordinates of the center of the circle.
- \( r \) is the radius of the circle.
Coordinate Geometry
Coordinate geometry, also known as analytic geometry, is the study of geometry using a coordinate system. This modern approach connects algebra with geometry and allows for the solution of geometric problems using equations. In this framework,
- points are defined by coordinates \((x, y)\)
- the position of these points is determined numerically by their distance from axes
Finding Center and Radius
When given a circle's equation in expanded form, such as \[16x^2 + 16y^2 - 64x + 32y + 55 = 0\],determining the center and radius involves a method known as completing the square. This process helps to transform the equation into the standard circle equation format.The steps are as follows:
- Group and rearrange the terms: Gather the \(x\) and \(y\) terms together.
- Apply completing the square: This involves rewriting the quadratic expressions in both \(x\) and \(y\) such that they form perfect squares.
- Simplify and solve: Adjust the equation to match the standard form \((x-h)^2 + (y-k)^2 = r^2\).