How do you write equations for 4 lines that intersect to form the sides of a parallelogram? What must be true about such lines?

To write equations for the four lines that form the sides of a parallelogram, we need to know some properties of parallelograms and lines.

1. Property of a parallelogram: Opposite sides are parallel.
2. Property of parallel lines: They have the same slope.
3. Property of a parallelogram: Consecutive sides are equal in length.
4. Property of a line: The equation of a line can be determined using either the slope-intercept form or the point-slope form.

Now, let's go through the steps to write the equations:

Step 1: Determine the slope of one of the lines.
- This can be done by finding the change in y-coordinates divided by the change in x-coordinates between two points on the line.

Step 2: Use the slope to write the equation of the line.
- You can use either the slope-intercept form (y = mx + b) or the point-slope form (y - y1 = m(x - x1)).

Step 3: Find the equation of the parallel line with the same slope.
- Since the opposite sides of a parallelogram are parallel, any two lines that are opposite to each other will have the same slope.

Step 4: Determine the equation of the other two lines using the properties of a parallelogram.
- The consecutive sides of a parallelogram are equal in length, so we can find the equations of the remaining lines by finding the equations of the parallel lines passing through the endpoints of the first line.

By following these steps, you can find the equations for the four lines that form the sides of a parallelogram.