Slope-Intercept Equation of a Line
Example 1: Write the equation of a line with y-intercept (0, 2) and slope of 4/5
y = mx + b
m = 4/5
Example 2: Graph the equation y 
answer: y 
b=2
4
x2
5
4
x2
5
The first point that you plot is the y-intercept (0, 2)
From there, rise up 4 and run right 5
second point will be (5, 6)
Example 3: Graph the equation 4x + y = 6
First “rearrange the furniture”
y = − 4x + 6
hop and swap the 4x
slope = − 4 or – 4/1
y-intercept is (0, 6)
The first point that you plot is the y-intercept (0, 6)
If the slope is negative, go down instead of up, but still run right.
From there, drop 4 and run right 1
second point will be (1, 2)
Example 4: Write the equation of the line: m = 3; passing through (- 2, 4).
We’re given m = 3; x = - 2; y = 4 (we know x and y from the ordered pair)
y = mx + b
4 = 3(- 2) + b
4=-6+b
10 = b
Now plug m and b into the equation y = 3x + 10
Example 5: Write the equation of a line parallel to y = 3x + 7 thru (- 2, 4)
This is the same problem as Example 4 but you have to know that parallel
lines have equal slopes
Slope-Intercept Equation of a Line
Reminder:
Horizontal lines are y = #
Vertical lines are x = #
Example 6: Write the equation of a line parallel to the x-axis through the point (5, 6)
x-axis and all lines parallel to it are horizontal
y = # so
y=6
Example 7: Write the equation of a line parallel to the y-axis through the point (5, 6)
y-axis and all lines parallel to it are vertical
x = # so
x=5