⇒ β=1 let coordinate of c be (h,Q). C bisects PR Coordinate of R is (−α+2h,−1) Points R lies on the circle x2+y2−αx−y=0 ⇒ (−α+2h)2+1−α(−+2h)−(−1)=0 ⇒ α2+4h2−4αh+1+α2−2hαz+1=0 4h2−6αh+2α2+2=0 D>0 ⇒ 36α2−×4×2(α2+1)>0 ⇒ 26α2−32α2−32>0 ⇒ 4α2−32>0⇒α2>8