Suppose you had two circles one has a center of A and a radius AB, the second one has a center of C with a radius of CD construct the two circles so that
it has one point two points and no points in common



1) One point in common, if B=D (circles stick in a common point between AB and CD) OR if A=C and AB > CD (then circles have a common center, but CD circle is inside the AB circle)

2) No points in common, if CD is inside AB, but C nor D doesn't stick with A nor B OR CD is outside AB and D doesn't stick with B (two different circles - one next to another)

3) Two common points, if C is between A and B (the circles make kind of "wedding ring" symbol)

4) More than two common points, if AB=CD (one circle lays exatcly on the second one - infinite common points) OR if A=D and C=B (again "wedding ring" symbol, but with center A on circuit D and center C on circuit B - four common points)

If it looks chaotic, try to draw it - it should help.