What's My line?

Target Curriculum: Mathematics

Target Grade: 8

SOLs: MAT.ALG.6   MAT.ALG.7  
Time: 2/ 45 minute periods

Objective:
Students will identify and determine equations of a line from graphs of lines.

Purpose:
Give students on hand experience identifying equations of a line by using the slope and y-intercept, two points on a line, or the slope and a point on the line.

Materials:
Overhead projector, coordinate grid transparency, metric ruler, projector pens, index cards, pencil, paper, graphing calculator, and deck of cards.

Procedure:
#1. Students will be divided into groups of 4 or 5. In each group, students will select cards to find who will be first , second, etc. to draw graph of a line when the group is selected. #2 Now have each group select a card from the deck to see who will have the first turn at drawing the lines given certain criteria listed on individual index cards. #3 The teacher will need to write criteria for graphing a line on each index card. Use a wide variety of criteria such as two points on a line, slope and a point, slope and y-intercept, horizontal lines, vertical lines, etc. Make a class set of cards. #4 Now it's time to start the competition! The first group will select an index card and proceed to draw the line on the overhead transparency grid. #5 Members on each team will now begin to find the equation of this line drawn and raise their hands to be the first to verify their equations. #6 The group selected will share the equation with the class after they have verified its correctness by entering it in a graphing calculator. One person from the group must explain how they derived the linear equation. If it is correct, they will receive 10 points. #7 Action will proceed to the next group who will draw an index card and then draw the line. Groups will determine the equation of the line. #8 Tally the points earned by each group. Treats may be given to the winners.

Observations:
Pre-requisite Skills: * find the slope & y-intercept * Identify and use slope-intercept form to write equations of lines * Find the equation of a line using two points on the line. *Using the graphing calculator to graph linear equations.

Conclusions:
This is a great activity to review writing linear equations and can be applied to other concepts.

Extension:
Have students create their own lines; enter them on the overhead; have others identify the equation of the lines.

Class Discussion Questions:
What method did you select to write the equation of the line? Is there one method you favor and why?