Q. A circle of radius 5 touches another circle $x^{2} + y^{2} - 2x - 4y - 20 = 0$ at (5, 5), then its equation is
A) $x^{2} + y^{2} + 18x + 16y + 120 = 0$
B) $x^{2} + y^{2} - 18x - 16y + 120 = 0$
C) $x^{2} + y^{2} - 18x + 16y + 120 = 0$
D) None of the above
Explanation
(b)
Obviously, point (5, 5) lies only on the circle $x^{2} + y^{2} - 18x - 16y + 120 = 0$, also radius of this circle is 5
Hence, option (b) is correct
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.