AP EAMCET2010MathematicsCircle
The equation of the radical axis of the pair of circles 7 x^2+7 y^2-7 x+14 y+18=0 and 4 x^2+4 y^2-7 x+8 y+20=0 is
Options
- Ax-2 y-5=0
- B2 x-y+5=0
- C21 x-68=0
- D23 x-68=0
Correct answer
C. 21 x-68=0
Step-by-step solution
Let S₁ x^2+y^2-x+2 y+ 18 7 =0 and S₂ x^2+y^2- 7 4 x+2 y+5=0 Now, the radical axis of the pair of circles are S₁-S₂=0 (x^2+y^2-x+2 y+ 18 7 )- (x^2+y^2- 7 4 x+2 y+5 )=0 -x+ 7 4 x+ 18 7 -5=0 -x+ 7 4 x- 17 7 =0 -28 x+49 x-68=0 21 x-68=0