The Slope of A Line
|The Angle From the Horizontal - Rise Over Run|
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.
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.
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.
You can also express the slope of a line with the coordinates of points on the line. For instance, in the above figure, A(x, y) and B(s, y) 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
That is it!!!
Try Algebra for more interesting concepts.