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# Dueling Methods for Writing the Equation of a Line

Lesson 8 of 20

## Objective: SWBAT write the equation of a line using the slope-intercept form and point-slope form.

#### Warm up

*10 min*

Today's Warm up is intended for the students to complete in 5 minutes. It sets up the introduction of a new model for linear functions. I have not introduced the point-slope form to write the equation of a line previously. Therefore, I instruct my students to complete only the left side of the comparison chart. In other words, I expect my students to write the equation of a line using slope-intercept form, y=mx + b.

After my students complete the Warm Up, I will demonstrate point-slope form by completing the right side of the comparison chart. I encourage my students to take notes as they follow along and complete the right side of the table with me. I demonstrate introducing the Warm Up and using Point-Slope form in the following video:

#### Resources

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#### Independent Practice

*15 min*

I want to give my students a lot of time for practice today, so I will allow them to work on the Independent Practice until there are about 10 minutes left in the period. The Independent Practice is similar to the Warm-up: students to write the equation of a line using slope-intercept form on one side of the worksheet. On the other side, they use point-slope form.

Because I want students to recognize linear relationships in different forms, in this practice students to write the equations of the lines from different representations:

- a linear graph
- a point and a slope
- two points
- an x-intercept and a slope
- two points with the same x value
- a table

At the end of the Independent Practice I provide a **Select All** type multiple choice question. Students will be assessed in this format on the PARCC Exam this year.

With about 10 minutes left in the period, I instruct the students to complete the Independent Practice as homework to be handed in the next day and we move on to today's Exit Slip.

#### Resources

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#### Exit Slip

*10 min*

Today's Exit Slip requires about 10 minutes. It provides me with a quick formative assessment to check student understanding of using Point-Slope Form to write the equation of a line. The students are instructed to use Point-Slope Form, but I expect some students will apply Slope-Intercept Form.

**Examples of Student Work**

- Student 1 solved the equation correctly for the y intercept, but then wrote y=3x -17.
- Student 2 calculated the wrong slope and then distributed incorrectly to the 2nd term in the parentheses.
- Student 3 wrote the correct equation y=3x + 17

Based on the examples shown here, I learned that it will be important to emphasize precision (MP6) in future lessons because many errors were small and resulted from a lack of precision in the application of a method.

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- UNIT 1: Introduction to Functions
- UNIT 2: Expressions, Equations, and Inequalities
- UNIT 3: Linear Functions
- UNIT 4: Systems of Equations
- UNIT 5: Radical Expressions, Equations, and Rational Exponents
- UNIT 6: Exponential Functions
- UNIT 7: Polynomial Operations and Applications
- UNIT 8: Quadratic Functions
- UNIT 9: Statistics

- LESSON 1: Introduction to Sequences
- LESSON 2: The Recursive Process with Arithmetic Sequences
- LESSON 3: Recursive vs. Explicit
- LESSON 4: Increasing, Decreasing, or Constant?
- LESSON 5: Change Us and See What Happens!
- LESSON 6: Why are lines parallel?
- LESSON 7: Get Perpendicular with Geoboards!
- LESSON 8: Dueling Methods for Writing the Equation of a Line
- LESSON 9: Comparing Linear Combinations in Ax +By= C to y=mx +b
- LESSON 10: Equations for Parallel and Perpendicular Lines.
- LESSON 11: Assessment of Graphing Lines through Art!
- LESSON 12: Are x and y Directly or Inversely Proportional? (Day 1 of 2)
- LESSON 13: Are x and y Directly or Inversely Proportional? (Day 2 of 2)
- LESSON 14: Writing, Graphing, and Describing Piecewise Linear Functions
- LESSON 15: Introduction to Scatter Plots, Line of Best Fit, and the Prediction Equation
- LESSON 16: Predicting the Height of a Criminal (Day 1 of 2)
- LESSON 17: Predicting the Height of a Criminal (Day 2 of 2)
- LESSON 18: Predicting Bridge Strength via Data Analysis (Day 1 of 2)
- LESSON 19: Predicting Bridge Strength via Data Analysis (Day 2 of 2)
- LESSON 20: Linear Assessment