At the end of this lesson, students will be able to:
Identify the slope and intercept of equations and graphs.
Graph an equation in slope-intercept form.
Understand what happens when you change the slope or intercept of a line.
Identify parallel lines from their equations.
Terms introduced in this lesson:
Teaching Strategies and Tips
Use Examples 1 and 2 to make observations such as:
when a line slants downward and when it slants upward.
when a line is horizontal.
when the intercept is below the axis and when it’s above the axis.
when a line passes through the origin.
Use the slope-intercept method to graph lines as an alternative to plotting and joining two intercepts.
With a graphing utility, demonstrate the effects on a line when changing and one at a time in an equation in slope-intercept form. Make observations such as:
The larger the , the steeper the line.
Negative slopes can also represent steep lines. The smaller the (more negative), the steeper the line.
Slopes approximately equal to zero represent lines that are almost horizontal.
Changing the intercept shifts a line up/down.
Parallel lines have the same slope but different intercepts.
In Example 2, use the marked lattice points and/or intercepts in the slope calculation for each line. Using these points allows students to obtain exact answers. See also Review Questions, Problems 2 and 3.