Slope-Intercept Form
If you know the slope , and -intercept of a line (the point where the line crosses the -axis), you can write the equation of the line in slope-intercept form .
(You can think of this as a special case of the point-slope form of the equation where is the point .)
Example 1 :
Find an equation of the line in slope-intercept form with slope and -intercept .
.
Example 2 :
Find an equation of the line in slope-intercept form with -intercept and passing through the point .
First, find the slope of the line:
Then, write the equation:
Equations in this form are easy to graph, since the slope of the line is and the -intercept of the line is .
Example 3 :
Rewrite the equation in slope-intercept form.
The equation is already in point-slope form; we know that is the slope.
Expand the right side using the distributive property.
Add to both side.
Now we have the equation in slope-intercept form.
Example 4 :
Graph .
Since the equation is given in slope-intercept form, we know immediately that the line crosses the -axis at and has slope . We can quickly use the slope to find a second point , and graph the line.