JEE Main2014MathematicsCircleActual
The set of all real values of for which exactly two common tangents can be drawn to the circles x^2+y^2-4 x-4 y+6=0 and x ^2+ y ^2-10 x -10 y + =0 is the interval:
Options
- A(12,32)
- B(18,42)
- C(12,24)
- D(18,48)
Correct answer
B. (18,42)
Step-by-step solution
The equations of the circles are x^2+y^2-10 x-10 y+ =0 and x^2+y^2-4 x-4 y+6=0 aligned &C₁= centre of (1)=(5,5) & C ₂= centre of (2)=(2,2) &d= distance between centres &= C ₁ C ₂= 9+9 = 18 &r₁= 50- , r₂= 2 & For exactly two common tangents we & have &r₁-r₂ 18 or < 42 & Required interval is (18,42) & aligned