To find the slope of a line on a graph, follow these steps:
- Select Two Points on the Line
Choose any two points on the line, preferably points with integer coordinates for easier calculation. Label them as (x1,y1)(x_1,y_1)(x1,y1) and (x2,y2)(x_2,y_2)(x2,y2)
- Calculate the Rise and Run
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Rise is the vertical change between the two points: y2−y1y_2-y_1y2−y1.
-
Run is the horizontal change between the two points: x2−x1x_2-x_1x2−x1.
Note the direction: -
Rise is positive if you move up, negative if you move down.
-
Run is positive if you move right, negative if you move left
-
- Use the Slope Formula
Calculate the slope mmm using the formula:
m=riserun=y2−y1x2−x1m=\frac{\text{rise}}{\text{run}}=\frac{y_2-y_1}{x_2-x_1}m=runrise=x2−x1y2−y1
This ratio represents the steepness of the line
- Interpret the Slope
- A positive slope means the line rises as it moves from left to right.
- A negative slope means the line falls as it moves from left to right.
- A slope of zero means the line is horizontal.
- An undefined slope (division by zero) means the line is vertical
Example:
If you pick points (0,−3)(0,-3)(0,−3) and (5,1)(5,1)(5,1), the rise is
1−(−3)=41-(-3)=41−(−3)=4 and the run is 5−0=55-0=55−0=5. So the slope is
4/54/54/5
. This method works for any straight line on a graph and helps you understand how steep the line is
Summary
- Pick two points on the line.
- Calculate rise (change in y) and run (change in x).
- Divide rise by run to get the slope.
This is the standard way to find slope from a graph.