The equation of the circle having the lines y2−2y+4x−2xy=0 as its normals and passing through the point (2,1) is
y2–2y+4x–2xy=0
y(y–2)–2x(y–2)=0
y=2x,y=2 are normal to the circle and every normal passes through the center
Intersection of normal will give us center
y=2x,y=2⟹x=1
C = (1,2) and P = (2,1)
CP must be equal to radius
⟹r=√(2−1)2+(1−2)2=√2
Equation of circle having center (a,b) and radius r is (x−a)2+(y−b)2=r2
⟹(x−1)2+(y−2)2=2
⟹x2+y2−2x–4y+3=0