### What is the condition for two graphed lines in the coordinate plane to be parallel, or perpendicular? Is there a way to find out the slope with just two coordinate points? May I determine the slope of a line with just the graph?

### You have asked your self these questions several times. This lesson gives you the answers for all of them. Making use of colors and in a step by step mode. You will really find it fun and interesting! If you need to mark particular sections in the lesson you may use the MARKER TOOLS menu on the top of the screen. Some parts of the lesson are better understood if you review the definitions given below the lesson scrolling down the screen.

** Lesson's Content **

** Lesson's Glossary **

**Graph of a number: The location of a point paired with a number in the number line.**

Graph of an ordered pair: The location in the coordinate plane associated with an ordered pair of real numbers.

**Ordered pair: A pair of numbers for which the order of the numbers is important; (2, -3) is an ordered pair. **

Ordinate: The y-coordinate in an ordered pair of the coordinate plane.

Origin: The location of the zero point in a number line.

**Parallel lines: Lines in the same plane that do not intersect; nonvertical lines that have the same slope.**

**Perpendicular lines: Lines that intersect or cross at right angles. Multiplying the slopes of perpendicular lines always yield -1. **

**Plot a point: Locating and graphing an ordered pair of real numbers in the coordinate plane. **

**Slope of a line: The measure of how steep a line is. The change in y (rise) divided by the change in x (run). Slope = m**

**x-intercept: The x-coordinate of a given point for which the graph intersects the x-axis.**

**y-intercept: The y-coordinate of a given point for which the graph intersects the y-axis.**

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