andDeduce that the two circles touch each other. If the line of centres meets the circles in points P,Q,R, find the equation of the circle that has PR as diameter.

r1+r2=15

sq root of (9^2+12^2) =15

therefore we can say they touch. but dont understand the second bit.

I don't know how to find the equation from the diameter of 15 from PR

PLease show step by step working!

Many thanks!