SlopeIntercept Form of a Line
The line y = 3x  1 has slope 3. To find the yintercept of
this line, let x = 0 in y = 3x  1: y = 3(0)  1 = 1. The yintercept is
(0, 1). Its ycoordinate appears in the equation:
Because the slope and yintercept can be read from the equation when it is solved
for y, this form of the equation of the line is called slopeintercept form.
SlopeIntercept Form
The equation of a line in slopeintercept form is y = mx + b, where m is the slope and (0, b) is the yintercept.
Example 1
Writing an equation given its slope and yintercept
Write the slopeintercept form of the equation of the line shown in the
figure below.
Solution
From the figure we see that the yintercept is (0, 3). If we start at the yintercept and
move down 2 and 3 to the right, we get to another point on the line. So the slope is
. The equation of this line in slopeintercept form is
