Find the coordinates of A and B, and then find the AB linear equation y1= k1x+b.

According to the A and B coordinates, we can know the EF coordinates and get the EF linear equation Y2 = K2x+C.

K 1=k2 then two straight lines are parallel.

Or find the coordinate A(x 1, y 1) B(x2, y2) first.

Then e (x 1, 0) f (0, y2)

if(y2-0)/(0-x 1)=(y2-y 1)/(x2-x 1)

Then two straight lines are parallel.