We have been working on this for a long time and cannot use only 4 line segments to connect all the 9 dots of this square without lifting our pencil. Hopefully someone is more logical than us and will share their logic.
W W W W W W W W W Let this be 9 dot then W-----------W-----------W-------from here
W W W
W W W
D
draw a line to D so that line cover the 3rd W in the second row and 2nd w in the third row and after that draw from D to the first w in the first row and then draw a line passing through the 2nd w in the second row and 3rd w in the third row.The puzzle is solved