Question

If (1, 2) is a limiting point of a coaxial system of circles containing the circle `x^(2)+y^(2)+x-5y+9=0`, then the equation of the radical axis, is
A. `x+2y+9=0`
B. `3x-y+4=0`
C. `x+9y-4=0`
D. `3x-y-1=0`

Answer 1

Correct Answer - B
The equation of a member of the family of coaxial circles having (1, 2) as the limiting point is
`S_(1)=(x-1)^(2)+(y-2)^(2)=0 ` ...(i)
Another member of the family of coaxial circles is given as
`S_(2)=x^(2)+y^(2)+x-5y+9=0` ...(ii)
The radical axis of (i) and (ii) is
`S_(1)-S_(2)=0 rArr 3x-y+4=0`.