Download Lesson 3

Lesson 3.2 Revisiting Slope Notes
Slope - ____________ of the vertical change to the corresponding horizontal change.
In other words it is the ________________________________.
Given points (x1, y1) and (x2, y2),
m = y2 – y1 = change in y
x2 – x1
change in x
Try it! Find the slope of a line that goes through (6, 9) and (-2, 5)
Slope-Intercept Form
y = mx + b
Try it! The slope of a line is 2/3. The y-intercept is -5. Write the equation of the line
and name another point on the line.
Example Write the equation of the line that passes through the points (3,2) and (-9, 6)
Your Turn! Write the equation of the line that has a slope of -1/4 and goes through the
point (8, -9).
Example Graph y = (2/3)x + 3
Remember: You can always make a table!
Your Turn! Graph 2x + y = -2. THINK!
Standard Form of a Linear Equation
Ax + By = C
where A, B, and C are real numbers.
This is useful to find the X-Intercept and the Y-Intercept.
Remember** The x-intercept is the ordered pair ___________
The y-intercept is the ordered pair ___________
The equation of a vertical line is __________.
The equation of a horizontal line is __________.
Example Graph 3x + 2y = 12. Then change the equation to slope-intercept form and check
to make sure it is the same.
Your Turn! Graph -2x + 5y = -10. Then change the equation to slope-intercept form and
check to make sure it is the same.
Parallel Lines
If lines are parallel, then their slopes are ______________
Perpendicular Lines
If lines are perpendicular, then their slopes are
_______________________________________________________________.
*What if they were just negatives of each other? For example: 2/3 and -2/3.
What’s their relationship?
Example: Given the equation y = ¾x + 2, write and graph the equation of the line
that goes through
a. is parallel and goes through (0, 4)
b. is perpendicular and goes through (6, 1)
Your Turn! Write an equation for each line. Then graph the lines.
a. through (-1, 3) and perpendicular to
the line -5x + y = – 3
b. through (2,1) and parallel to the line
y = 2/3x + 8
c. vertical and through (5, -3)