In this lesson students will learn how to determine the equation of a line using two points. Students will be finding there answer and then graphing the equation in Activity Center to see if it they are correct.
Before the Activity
Start lesson by reviewing notes:
Finding the Equation of a Line in Slope and Y-Intercept Form
Slope and Y-Intercept Form: y=mx+b
General Form: Ax+By+C=0
Formulas for slope, m:
To find the equation of a line all you need is the slope and a point.
There are two different ways to do this after you have a point and the slope.
If you have two points?first find the slope using the two points.
Example: Find the equation of a line in slope and y-intercept form for the line that passes through the points (-2,3) and (2,-5).
Insert the slope and either point into the slope and y-intercept formula and determine the y-intercept. Then insert slope and y-intercept into the slope and y-intercept formula.
During the Activity
Get the students to find the slopes for the following examples. Use quick poll to see if they got the slope correct.
Ex 1. Determine the equation of a line that passes through (-4, 8) and (-3, -7).
Ex 2. Determine the equation of a line that passes through (-5,3) and (2,0).
Ex 3. Determine the equation of the line that passes through the points (-1, 4) and (7, -5).
Ex 4. Determine the equation of the line that passes through the points (-2, 6) and (3, -5).
1) Open activity center. Plot the points as a teacher for the first example. To do this: Select the List tab and enter the two points into the Add L1 and L2. Select the List-Graph tab and select configure plots. Choose your type of point and change the X-List to L1 and the Y-List to L2. Then to start the activity change the contribute to equations and in the options allow 1 equation per student, allow them to view graphs, allow them to resubmit and set current graph as background. Select that students start with empty equations.
2) Start the activity. After students have submitted go through the solution. Clear the activity data and repeat the steps for the next example.
After the Activity
As a class, discuss questions that appeared to be more challenging
Ex 1. Determine the equation of the line parallel to the x-axis and passing through
Ex 2. Determine the equation of the line that is perpendicular to and having the same y-intercept as .
Ex 3. Determine the equation of the line parallel to the y-axis and passing through
Ex 4. Determine the equation of a line that passes through A(4, 5) and is parallel to the line .
Ex 5. Determine the equation of a line that passes through A(3, 4) and is parallel to the line .
Ex 6. Determine the equation of a line with a slope of and passing through (-1, 6).
Re-teach concepts as necessary