Join 9 dots with only 4 straight lines

[robert551069]

Draw this pattern:-
. . .
. . .
. . .

Now try to join all the dots with a maximum of 4 straight lines without going over the same line twice.
For the solution see joindave.co.uk

[trt]

I know how to do it but hard to show you.

[mike11111]

At some point you need to extend one of the lines to the outside of the grid.

[trt]

Draw the first line beginning at dot 1 and continuing diagonally down and right, pass through dot 5 to reach dot 9.

From dot 9, the second line is drawn upwards, passing through dot 6 and dot 3 to end above dot 3.

The key to solving this puzzle with 4 straight lines joined continuously -- often described as "drawn without lifting the pencil off the paper" -- is to end the second line far enough above dot 3 that the third line drawn diagonally down and left will pass through dots 2 and 4, ending left of and level with dot 7.

Finally, the fourth and last line is drawn horizontally across to the right, passing through dots 7 and 8, ending back at dot 9.