Substitute x=my- 1 into y? =4x to get y? -4my+4 = 0；

So y 1+y2=4m y 1y2=4.

The equation of bd is y-y2 = (y1+y2) (x-x2)/(x2-x1) y-y2 = 4 * (x-y2 * y2/4)/y2-y1.

Let y=0 x=y 1y2/4= 1, then point f( 1, 0) is on the straight line bd.