Find the equation of a circle which is tangent to the x-axis at point (4, 0) and is tangent to line 3x-4y-17=0 Directed Distance, point slope formula... Ok so I knew that the x-axis is the equation y=0. I think but i am not sure that the directed distance between the tangent line 3x-4y-17=0 is equal to the distance form (4,0) to the center. So this is what you get.... Abs(3x-4y-17)/Square root(9+4) = Square root ((x-4)^2+(y)^2) But i am not sure how to get rid of the absolute value signs and i am not sure if this will get me anywhere. Will it get me to a dead end? If so, what do i do?