Skip to main content
Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 3, Problem 51

Give the center and radius of the circle described by the equation and graph each equation. Use the graph to identify the relation's domain and range. (x + 1)² + y² = 25

Verified step by step guidance
1
Recognize that the given equation is in the standard form of a circle: \( (x - h)^2 + (y - k)^2 = r^2 \), where \((h, k)\) is the center and \(r\) is the radius.
Rewrite the equation \( (x + 1)^2 + y^2 = 25 \) as \( (x - (-1))^2 + (y - 0)^2 = 5^2 \) to identify the center and radius clearly.
From the rewritten form, identify the center of the circle as \( (-1, 0) \) and the radius as \( 5 \).
To find the domain of the circle, consider the horizontal distance from the center: the domain is all \(x\) values such that \(x\) is between \(-1 - 5\) and \(-1 + 5\), or \([-6, 4]\).
To find the range of the circle, consider the vertical distance from the center: the range is all \(y\) values such that \(y\) is between \(0 - 5\) and \(0 + 5\), or \([-5, 5]\).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Standard Form of a Circle's Equation

The standard form of a circle's equation is (x - h)² + (y - k)² = r², where (h, k) is the center and r is the radius. Recognizing this form allows you to identify the circle's center and radius directly from the equation.
Recommended video:
5:18
Circles in Standard Form

Graphing Circles

Graphing a circle involves plotting its center and using the radius to mark points equidistant from the center in all directions. This visual representation helps in understanding the shape and position of the circle on the coordinate plane.
Recommended video:
5:18
Circles in Standard Form

Domain and Range of a Circle

The domain of a circle is the set of all possible x-values, and the range is the set of all possible y-values covered by the circle. For a circle centered at (h, k) with radius r, the domain is [h - r, h + r] and the range is [k - r, k + r].
Recommended video:
5:18
Circles in Standard Form