Graphing and Writing Equations of Circles

What does the equation of a circle primarily represent?

• A parabola

• Two curves

• An ellipse

• A straight line

How do you determine the center of a circle from its equation?

• By calculating the area

• By using the values of h and k in the equation

• By identifying the coefficients of x and y

• By finding the square root of the radius

How is the standard form of a circle's equation written?

• (x+h)^2 + (y+k)^2 = r

• x^2 + y^2 = r

• (x-h)^2 + (y-k)^2 = r^2

• x^2 + y^2 = r^2

In the equation of a circle, what does 'r' stand for?

• Diameter

• Circumference

• Radius

• Area

What does the equation x^2 + y^2 = r^2 imply about the circle?

• It does not exist

• It is an ellipse

• Its center is at (0, 0)

• Its radius is 0

What does the square of the radius in a circle's equation represent?

• The diameter of the circle

• The distance from the center to any point on the circle

• The area of the circle

• The circumference of the circle

What is the center of a circle with the equation (x-3)^2 + y^2 = 25?

• (3, 0)

• (-3, 0)

• (0, 3)

• (0, -3)

What is the radius of a circle whose equation is x^2 + (y+3)^2 = 9?

• 18

• 9

• 3

• 6

What is the center of a circle with the equation (x+3)^2 + (y-4)^2 = 16?

• (-3, 4)

• (3, -4)

• (3, 4)

• (-3, -4)

If a circle's equation is (x-2)^2 + (y+1)^2 = 9, what is its radius?

• 9

• 3

• 4

• 2