Equation of a Circle

  1. Which of the following is an equation of a circle in the $xy$ plane with center (3,0) and a radius with endpoint (6,4)?
    1. $(x-3)^2+y^2=36$
    2. $(x-3)^2+y^2=25$
    3. $(x-3)^2-y^2=16$
    4. $(x-3)^2-y^2=25$
  2. Which of the following is an equation of a circle in the $xy$ plane with center (0,-2) and a radius with an endpoint on the origin?
    1. $x^2+(y-2)^2=2$
    2. $x^2+(y-2)^2=4$
    3. $x^2+(y+2)^2=2$
    4. $x^2+(y+2)^2=4$
  3. $x^2+y^2-2x+6y=6$ is the equation of a circle in the $xy$ plane. What is the radius of the circle?
    1. 2
    2. 3
    3. 4
    4. 6
  4. $x^2+y^2+12x-10y=-12$ is the equation of a circle in the $xy$ plane. What is the radius of the circle?
    1. 3
    2. 5
    3. 7
    4. 9
  5. $x^2+y^2-8x+2y=-4$ is the equation of a circle in the $xy$ plane. What are the coordinates of the center of the circle?
    1. (-8,2)
    2. (8,-2)
    3. (4,-1)
    4. (-4,1)
  6. $x^2+y^2-3x-5y=-3$ is the equation of a circle in the $xy$ plane. What are the coordinates of the center of the circle?
    1. (1.5, 2.5)
    2. (6,10)
    3. (9,25)
    4. (6,-10)

Answer Key: