Can you find sets of sloping lines that enclose a square?
How does the position of the line affect the equation of the line?
What can you say about the equations of parallel lines?
Investigate what happens to the equations of different lines when
you reflect them in one of the axes. Try to predict what will
happen. Explain your findings.
What is the area, (in square units) of the triangle formed by the three lines whose equations are: $y-x=6$, $x-2y=3$ and $x+y=6$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.