Question

What is the standard form of the equation of the circle in the graph?

A. (x + 3)2 + (y + 3)2 =3
B. x2 + y2 = 3
C. (x + 3)2 + (y + 3)2 =9
D. x2 + y2 = 9

Answer 1

hints to find the equation of a circle given a graph:
step 1:
read off the graph the coordinates of the centre of the circle, (x0, y0), and the radius (length of half the diameter) r.
step 2:
Write the equation of the circle as:
\((x-x0)^2+(y-y0)^2=r^2\)
substituting x0, y0 and r from step 1.