Slope-Intercept Form of a Line
The line y = -3x - 1 has slope -3. To find the y-intercept of
this line, let x = 0 in y = -3x - 1: y = -3(0) - 1 = -1. The y-intercept is
(0, -1). Its y-coordinate appears in the equation:
Because the slope and y-intercept can be read from the equation when it is solved
for y, this form of the equation of the line is called slope-intercept form.
The equation of a line in slope-intercept form is y = mx + b, where m is the slope and (0, b) is the y-intercept.
Writing an equation given its slope and y-intercept
Write the slope-intercept form of the equation of the line shown in the
From the figure we see that the y-intercept is (0, 3). If we start at the y-intercept 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 slope-intercept form is