Circles?

1)The center of a circle is at (−3, 1) and its radius is 9.

What is the equation of the circle?

(x+3)2+(y−1)2=18

(x−3)2+(y+1)2=81

(x−3)2+(y+1)2=18

(x+3)2+(y−1)2=81

 

3)

The equation of a circle is (x+4)2+(y−5)2=121.

What is the center and radius of the circle?

center: (−4, 5); radius: 11

center: (4, −5); radius: 11

center: (−4, −5); radius: 121

center: (−4, 5); radius: 121

 

4)

The blueprints for a police station show that one of the lamp posts has a motion detector on it, and that the equation  (x+14)2+(y−6)2=9 describes the boundary within which motion can be sensed.

What is the greatest distance, in feet, a person could be from the lamp and be detected?

3 ft

6 ft

9 ft

81 ft

 

5)

Carlos plots a circular planter's wall on a computer. He determines that the circle that defines the part of the planter wall that gets watered by the sprinkler is (x−10)2+(y+12)2=36.

What is the diameter, in meters, of the circular area that gets watered by the sprinkler?

36 m

12 m

6 m

3 m