Solution
= Solution
The <circles> have centres $(1,1)$ and $(-1,1)$. Their <Euclidean distance> is
$$
\boxed{\sqrt{(1-(-1))^2+(1-1)^2}=2}.
$$
= Solution
The <circles> have centres $(1,1)$ and $(-1,1)$. Their <Euclidean distance> is
$$
\boxed{\sqrt{(1-(-1))^2+(1-1)^2}=2}.
$$