To test your knowledge, try to answer the following practice problem:
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What is the equation of the circle pictured below? |
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The center is given in the image: (–2, –1). All you need to finish the formula is the radius. We determine this by finding the distance from the center and the point, (2, –4), pictured on the circle:
The radius of the circle is 5, so the equation of the circle can be written as (x + 2)2 + (y + 1)2 = 25.
