The equation for the circle is x2+y2=9 what is the length of the radius.?
a: 9
b: 6
c: 3
d: 81

The general form of the Cartesian graph of a circle is x^2 + y^2 = r^2, where r is the radius of the circle. By direct comparison with the graph in question, we see that r^2 = 9.

Therefore r is the principal square root of 9. r = 3, so the answer is C. I hope this helps you :)