【官方】SAT数学每日一题附答案和解析(2018年1月24日)

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Math: Calculator Permitted

Read the following question and then select the best answer.

A circle in the x y-plane has its center at (-100,221)and a diameter of 17.

Which of the following is an equation of the circle?

Select an Answer

Answer

A

(x+100)2+(y-221)2=72.25

Answer

B

(x+100)2+(y-221)2=289

Answer

C

(x-100)2+(y+221)2=72.25

Answer

D

(x-100)2+(y+221)2=289

答案及解析：

A

EXPLANATION

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

In standard form, the equation of this circle is:

(x+100)2+(y-221)2=72.25

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