1) The radical centre of the circle x2+y2−4x−6y+5=0, x2+y2−2x−4y−1=0 and x2+y2−6x−2y=0=0 lies on the line A) x+y-5=0 B) 2x-4y+7=0 C) 4x-6y+5=0 D) 18x-12y+1=0 Answer: Option DExplanation: S1=x2+y2−4x−6y+5=0 S2=x2+y2−2x−4y−1=0 S3=x2+y2−6x−2y=0 S1−S2=0⇒2x+2y−6=0⇒x+y−3=0 .....(i) S2−S3=0⇒4x−2y−1=0 ......(ii) Solving Eqs.(i) and (ii) , we get x=76,y=116 (76,116) satisfies the equation 18x-12y+1=0