Question

A circle has the equation x2+ y2 = 9. What is the length of the radius?

Answer 1

3

Explanation:

The standard form of the equation of a circle is

( x − a ) ^2 + ( y − b ) 2 = r ^2

where (a,b) are the coords of the centre and r , the radius.

x ^2 + y ^2 = 9

is in this form with a = b = 0 and r = 3

Answer 2

The center is (0,0) and the radius is 3

Explanation:

The equation of a circle is given by

(x-h)^2+(y-k)^2 = r^2

Where (h,k) is the center and r is the radius

(x-0)^2+(y-0)^2 = 3^2

The center is (0,0) and the radius is 3