AP EAMCET201920 Apr 2019Evening ShiftMathematicsCircleActual
The number of common tangents to the circles x^2+y^2+4 x-6 y-12=0 and x^2+y^2-8 x+10 y+5=0 is
Options
- A4
- B3
- C2
- D1
Correct answer
C. 2
Step-by-step solution
Equation of given circles array r S₁: x^2+y^2+4 x-6 y-12=0 and S₂: x^2+y^2-8 x+10 y+5=0 array Centre of S₁ is C₁(-2,3) and radius of S₁ is r₁=5 and centre of S₂ is C₂(4,-5) and radius of S₂ is r₂=6 . aligned & C₁ C₂= (4+2)^2+(-5-3)^2 = 36+64 =10 & and r₁+r₂=5+6=11 & r₁+r₂>c₁ c₂ aligned There are only two common tangent to circle S₁ and S₂ . Hence, option (c) is correct.