The given circles are S1≡x2+y2+3x+7y+2p−5=0.....(1) S2≡x2+y2+2x+2y−p2=0.....(2) ∴ Equation of common chord PQ is S1−S2=0 ⇒L≡x+5y+p2+2p−5=0 ⇒ Equation of circle passing through P and Q is S1+λL=0 ⇒(x2+y2+3x+7y+2p−5)+λ (x+5y+p2+2p−5)=0 As it passes through (1,1), therefore ⇒(7+2p)+λ(2p+p2+1)=0 ⇒λ=−