圓的方程 ( 位於以原點為圓心的圓上 )

Distance between A and (0,0) = sqrt[49 + 81] = sqrt130.
Distance between B and (0,0) = sqrt[121 + 9 ] = sqrt130.
So A and B are on the same circle with (0,0) as centre.
Equation is :
x^2 + y^2 = 130.

AB = diameter?