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Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 3, Problem 39

Write the standard form of the equation of the circle with the given center and radius. Center (-4, 0), r = 10

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Recall the standard form of the equation of a circle is given by: \( (x - h)^2 + (y - k)^2 = r^2 \), where \( (h, k) \) is the center and \( r \) is the radius.
Identify the center \( (h, k) \) from the problem: here, the center is \( (-4, 0) \), so \( h = -4 \) and \( k = 0 \).
Substitute the values of \( h \) and \( k \) into the standard form: \( (x - (-4))^2 + (y - 0)^2 = r^2 \).
Simplify the expression inside the parentheses: \( (x + 4)^2 + y^2 = r^2 \).
Substitute the radius \( r = 10 \) and square it to get \( r^2 = 10^2 = 100 \), so the equation becomes \( (x + 4)^2 + y^2 = 100 \).

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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. This form directly relates the coordinates of any point on the circle to its center and radius.
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Coordinates of the Center

The center of the circle is given as a point (h, k). In the equation, these values are used as (x - h) and (y - k) to measure the horizontal and vertical distances from the center to any point on the circle.
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Radius and Squaring

The radius r is the distance from the center to any point on the circle. In the equation, the radius is squared (r²) to relate it to the sum of the squared distances along the x and y axes, ensuring all points satisfy the circle's definition.
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