Circles: equations and tangents

Question 1 of 10

x² + y² = 25 has radius 25.

Question 2 of 10

Find the radius of the circle x² + y² + 2x − 4y − 31 = 0.

Question 3 of 10

The radius of the circle x² + y² = 9 is ___

Question 4 of 10

Show that the line y = x + 2 is a tangent to the circle x² + y² = 2.

Question 5 of 10

Write down the equation of the circle with centre (−4, −2) and radius 5.

Question 6 of 10

Find the equation of the tangent to the circle x² + y² = 25 at the point (3, 4).

Question 7 of 10

The point (3, 4) lies on x² + y² = 25.

Question 8 of 10

The centre of x² + y² + 2gx + 2fy + c = 0 is

Question 9 of 10

The radius of x² + y² + 2gx + 2fy + c = 0 is

Question 10 of 10

Write down the equation of the circle with centre (−2, 4) and radius 4.