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Parallel Lines

How does the position of the line affect the equation of the line? What can you say about the equations of parallel lines?

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Perpendicular Lines

Position the lines so that they are perpendicular to each other. What can you say about the equations of perpendicular lines?

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Weekly Problem 35 - 2007

What is the area of the triangle formed by these three lines?

Enclosing Squares

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Here's a problem to work at with your graphic calculator or graph-plotting package on a computer.

If you plot the following lines

$\begin{eqnarray} y &=& 2x + 1\\ y &=& 2x + 4 \\ y &=& -0.5x + 1\\ y &=& -0.5x + 2.5 \end{eqnarray}$

the lines will enclose a square.

Can you find other sets of sloping lines that enclose a square?

If you are given the equations of two parallel lines

$y = ax + b$ and $y = ax + c$

can you explain how to find the equations of the other two lines that would enclose a square, if you know that one of the vertices is at $(0,b)$?

[In the example at the top, $a = 2$, $b = 1$ and $c = 4$]