This statement of the applicable relation is perhaps a little different than the one(s) you may have seen: From the point where the segments meet, the product of the length of segment to one side of the circle and the length of segment to the other side of the circle is the same for both segments. When the segment is tangent to the circle, those two circle intersection points are the same point.
This rule is applicable for all of these problems. Once the relation is written, the equation can be divided by the coefficient of x to find the value of x.
