Solution to Example
 What is the slope of the line given in the graph? Step One: Identify two points on the line. Let's calculate the slope of the line in the graph above using the points A (1, 2) and B (3, 6). Step Two: Select one to be (x1, y1) and the other to be (x2, y2). Let's take A (1, 2) to be (x1, y1). Let's take the point B (3, 6) to be the point (x2, y2). Step Three: Use the equation to calculate slope.
Therefore, the slope of our line is 2. This means for each positive change of 1 unit in the x variable, the y variable will increase 2 units. Remember, you can choose any two points on the line to calculate the slope. Using the graph above, calculate the slope using the Origin (0, 0) and point R (2, 4). If the Origin (0, 0) is selected to be (x1, y1) and R (2, 4) to be the point (x2, y2), our resulting slope comes out to be:

Again the slope is 2. You will find that regardless of what two points you choose on a given straight line to calculate a slope, your answer will always be the same. The slope for a given line is a constant.