Conic sections practice

Properties of circles worksheets

Find exact circle centers and positive radii from standard and rearranged general equations using whole numbers, fractions and radicals.

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Find the exact center and positive radius of each circle.

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Complete two squares to reveal the circle

Each worksheet contains ten circle equations. Choose whole numbers, fractions, radicals or a coherent mixture, then practice standard form, rearranged general form or five of each.

For x² + y² + Dx + Ey + F = 0, the center is (−D/2, −E/2). Substitute those exact coordinates to find radius squared, then take the positive square root.

The separate key repeats each equation, gives the exact center and radius, and shows the equivalent standard form.

Learning objective

What this activity builds

Recover a circle’s exact center and positive radius from standard form or a normalized general equation.

Worked example

Find the center and radius of x² + y² − 6x + 4y − 12 = 0.

Center (3, −2), radius 5.

Complete each square: (x − 3)² + (y + 2)² = 25.

Teaching notes

Make the practice count

  • In general form, halve each linear coefficient and change its sign to find the center.
  • Compute radius squared before taking the positive square root.
  • Move terms carefully when the two square terms appear on different sides.
  • Keep fractional and radical values exact.

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Choose one or more exact value types and the equation form, then change the seed for a reproducible set of ten circles.

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Math SheetNameScore/ 20TeacherDateProperties of CirclesFind the exact center and positive radius of each circle.1.x2+y2=121Center: ____________________ Radius: ____________________2.y2+22·y+20·x=-1·x2-52Center: ____________________ Radius: ____________________3.x-1342+y+522=1009Center: ____________________ Radius: ____________________4.-5·x+83·y-365144=-1·x2-1·y2Center: ____________________ Radius: ____________________5.x-1·72+y+132=3Center: ____________________ Radius: ____________________6.x2+y2-2·10·x=-19+2·14·yCenter: ____________________ Radius: ____________________math-sheet.comPage 1 / 2
Math SheetNameScore/ 20TeacherDateProperties of CirclesFind the exact center and positive radius of each circle.7.x-42+y+32=36Center: ____________________ Radius: ____________________8.x2+y2+2·x-143=0Center: ____________________ Radius: ____________________9.x+742+y-1122=1009Center: ____________________ Radius: ____________________10.x2=-1·y2+13·x+23·y-5875144Center: ____________________ Radius: ____________________math-sheet.comPage 2 / 2

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