Circles ⇒x2+y2−4x−6y+5=0 ... (S1) and x2+y2−2x−4y−1=0 ... (S2) Equation of radical axis is S1−S2=0 L1:(x2+y2−4x−6y+5)−(x2+y2−2x−4y−1)=0 ⇒−2x−2y+6=0 ⇒L1:x+y−3=0 Similarly, L2:(x2+y2+2x+2y−7)−(x2+y2+x+y+9)=0 ⇒L2:x+y−16=0 From Eqs. (i) and (ii), we obtain {m=