(b) Let centre of circle on X-axis be (K, 0). ∴ the radius of circle will be K.
∴ the equation of circle having centre (K, 0) and radius K is (x−K)2+(y−0)2=K2 ⇒ x2+K2 - 2hx + y2=K2 ⇒ x2−2Kx+y2 =0 ...(i) On differentiating both sides w.r.t x, we get 2x−2K+2y
dy
dx
=0 ⇒ K=x+y
dy
dx
......(ii) From equations (i) &( ii) we get x2−2(x+y