=0 ‌⇒‌‌x−y+1=0‌‌‌⋅⋅⋅⋅⋅⋅⋅(i) Radical axis of s ands′′:s−s′′=0 ⇒‌‌4x−y+7=0‌‌‌⋅⋅⋅⋅⋅⋅⋅(ii) From Eqs. (i) and (ii), we have x=−2,y=−1 ∴ Radical centre isP(−2,−1) Length of tangent fromPtos′ ‌=√(−2)2+(−1)2+‌
