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Mathematics

A circle in the xy-plane has its center at (-100,221) and a diameter of 17. Which of the following is an equation of the circle?

A.(x+100)2+(y-221)2=72.25
B.(x+100)2+(y-221)2=289
C.(x-100)2+(y+221)2=72.25
D.(x-100)2+(y+221)2=289

答案和解析

答案：B

解析：

The formula for a circle with a center at (h,k) and a radius of r is: (x-h)2+(y-k)2=r2

The length of the radius is half of the length of the diameter.

1/2*17=8.5

Using the coordinates of the center and the length of the radius of this circle in the equation yields: (x-(-100))2+(y-221)2=8.52

In standard form, the equation of this circle is: (x+100)2+(y-221)2=72.25