Analysis: It is known that M and N are the median lines of AB side and AC side of △ABC, so it is known that point C is on M and point B is on N;

Solution: Let the coordinates of point B be [b, 1] and the coordinates of point C be [2y- 1, y];

M is the midline of AB, so the coordinate of O at the midpoint of AB is [[b+1] ÷ 2,2]; So we can know the coordinates of B [5, 1]. Similarly, we can know that the coordinates of point C are: [-3, 1].

The equation of a line with BC edge is 4y-x- 1 = 0.