Video:How to Find the Slope of a Line

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Transcript:How to Find the Slope of a Line

When the slope of the line is 0, you know that the line is horizontal and you know it's a vertical line when the slope of a line is undefined. So, how do you calculate the slope of a line?

Instructions for How to Find the Slope of a Line

In the Figure below, the subscripts on point A, B and C indicate the fact that there are three points on the line. The change in y whether up or down is divided by the change in x going to the right, this is the 'rise over run' concept.

Equation for Finding the Slope of a Line

y = mx + b is the equation that represents the line and the slope of the line with respect to the x-axis which is given by tan  (read as tan theta) = m. This is the slope-intercept form of the equation of a line. When the slope passes through a point A(x1, y1) then y1 = mx1 + b or with subtraction y - y1 = m (x - x1) You now have the slope-point form of the equation of a line.

More Information About How to Find the Slope of a Line

You can also express the slope of a line with the coordinates of points on the line. For instance, in the above figure, A(x1, y1) and B(x2, y2) are on the line y= mx + b : m = tan q = therefore, you can use the following for the equation of the line AB: The equations of lines with slope 2 through the points would be: For (-2,1) the equation would be: 2x - y + 5 = 0. For (-1, -1) the equation would be: 2x - y + 1 = 0

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