x1^2+y1^2=13^2
x2^2+y2^2=19^2
(x1+x2)^2+(y1+y2)^2=24^2
(x1-x2)^2-(y2-y1)^2=2(13^2+19^2)-24^2=22^2
|a-b|=22
x1^2+y1^2=13^2
x2^2+y2^2=19^2
(x1+x2)^2+(y1+y2)^2=24^2
(x1-x2)^2-(y2-y1)^2=2(13^2+19^2)-24^2=22^2
|a-b|=22