the ones that have
the point in the y axis
They are the common tangents to the circles.
Which point is not located on the xaxis or the yaxis of a coordinate grid?Read more:Which_point_is_not_located_on_the_xaxis_or_the_yaxis_of_a_coordinate_grid
it intersects the segment joining the centers of two circles
A square does have a centre.
you draw a triangle formed by the centers of the two circles and use pythagoean theorem