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Section 3.3 : Circles


  1. Write the equation of the circle with radius 1 and center \(\left( {11,4} \right)\).
  2. Write the equation of the circle with radius 10 and center \(\left( { - 6,0} \right)\).
  3. Write the equation of the circle with radius \(\sqrt {19} \) and center \(\left( {7, - 2} \right)\).
  4. Write the equation of the circle with radius \(\frac{7}{3}\) and center \(\displaystyle \left( { - \frac{1}{2},\frac{3}{4}} \right)\).

For problems 5 – 10 determine the radius and center of the circle and sketch the graph of the circle.

  1. \({\left( {x + 8} \right)^2} + {y^2} = 36\)
  2. \({\left( {x - 1} \right)^2} + {\left( {y - 7} \right)^2} = 16\)
  3. \({\left( {x + 10} \right)^2} + {\left( {y - 6} \right)^2} = 25\)
  4. \(\displaystyle {x^2} + {\left( {y + 4} \right)^2} = \frac{{49}}{{144}}\)
  5. \({\left( {x + 2} \right)^2} + {\left( {y - 1} \right)^2} = 3\)
  6. \({\left( {x - 5} \right)^2} + {\left( {y - 3} \right)^2} = 11\)

For problems 11 – 17 determine the radius and center of the circle. If the equation is not the equation of a circle clearly explain why not.

  1. \({x^2} + {y^2} - 8y = 0\)
  2. \({x^2} + {y^2} - 6x - 4y - 12 = 0\)
  3. \({x^2} + {y^2} + 12x + 2y + 28 = 0\)
  4. \(16{x^2} + 16{y^2} - 16x + 8y - 11 = 0\)
  5. \(2{x^2} + 2{y^2} - 3x + 1 = 0\)
  6. \({x^2} + {y^2} + 2x - 2y + 11 = 0\)
  7. \({x^2} + {y^2} - 10x + 4y + 29 = 0\)