每日一题

Mathematics

A circle in the xy-plane has a center at (1,-6) and a diameter of 18. Which of the following is the equation of the circle?

A.(x+1)^2+(y-6)^2=324
B.(x+1)^2+(y-6)^2=81
C.(x-1)^2+(y+6)^2=324
D.(x-1)^2+(y+6)^2=81

答案和解析

答案：D

解析：

Choice D is correct.