If the point P (2, 1) lies on the line segment joining points A (4, 2) and B (8, 4), then
Given,
Point P (2, 1) lies on the line segment AB, joining the points A (4, 2) and B (8, 4);
Now,
The distance between A (4, 2) and P (2, 1),
By using the distance formula;
∵ Distance between two points (x1, y1) and (x2, y2),
d =
AP =
Distance between A (4, 2) and B (8, 4)
AB
Distance between B (8, 4) and P (2, 1),
BP =
∴ AB =
2AP = AB
Hence, required condition is AP =