Question

Which equations represent circles that have a diameter of 12 units and a center that lies on the y-axis? Select two options.

x2 + (y – 3)2 = 36
x2 + (y – 5)2 = 6
(x – 4)² + y² = 36
(x + 6)² + y² = 144
x2 + (y + 8)2 = 36

Answer 1

Answer: option (a) and option (e).

Explanation:

Answer 2

(a) and (e) are correct

Explanation:

(a) x² + (y - 3)² = 6²

(b) x² + (y - 5)² = (√6)²

(c) (x - 4)² + y² = 6²

(d) (x + 6)² + y² = 12²

(e) x² + (y + 8)² = 6²

The general equation of a circle is:

(x - a)² + (y - b)² = r², where (a, b) represents the x-y coordinates of the centre, and r represents the radius.

Hence, by process of elimination, the options that have a diameter of 12 units and therefore, a radius of 6 units, are (a), (c), and (e).

Therefore, the correct choices are (a), and (e), as (c) has a circle centre of (4,0) and does not lie on the y-axis.