X∧2+y∧2-2x-4y+m=0 is simplified as: (x- 1) 2+(y-2) 2 = 5-m, so the center of the circle is (1, 2), and we can know the straight line X-Y. OM is vertical, so the origin o is on the circle. Bring (0,0) into the equation of a circle and get m=0.