Some of you might try to connect all the points forming a square, like in the figure below, but one of the dots is not connected.
Some might connect the dots like the figures below, but five (5) lines were used instead of four (4) lines only.
Some might connect all the points like the figure below. Four lines were used but the lines are not connected. Though they are connected at the middle, the lines might be drawn with retracing or lifting the pen used.
There are still a lot of possible ways others may try but some may violate the condition specified.
Actually, there are four (4) possible solutions for this puzzles, depending on which point you will start with. I will just show one of the solutions and you do the rest. Just simply change the starting dot. You would notice that the figures will look the same but differ in direction.
As you notice, the lines are extended but it does not violate any of the conditions specified in the puzzle.
Now I'll leave you a puzzle similar to this puzzle. Here are twelve (12) dots. Your goal is to connect all of them by using five (5) lines only without lifting your pens, without retracing, and forming a closed path - the last segment must stop at where the first segment started.