Linear Relationships

Lesson 7

Math

Unit 5

8th Grade

Lesson 7 of 15

Objective


Determine slope from coordinate points. Find slope of horizontal and vertical lines.

Common Core Standards


Core Standards

  • 8.EE.B.6 — Use similar triangles to explain why the slope m is the same between any two distinct points on a non-vertical line in the coordinate plane; derive the equation y = mx for a line through the origin and the equation y = mx + b for a line intercepting the vertical axis at b.
  • 8.F.B.4 — Construct a function to model a linear relationship between two quantities. Determine the rate of change and initial value of the function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. Interpret the rate of change and initial value of a linear function in terms of the situation it models, and in terms of its graph or a table of values.

Foundational Standards

  • 7.NS.A.1
  • 7.NS.A.2.B

Criteria for Success


  1. Find the slope of a line using values represented in a table.
  2. Find the slope of a line that passes through two given coordinate points.
  3. Understand the slope of a horizontal line is 0 and the slope of a vertical line is undefined. 

Tips for Teachers


In determining slope from coordinate points, students will need a strong grasp of adding and subtracting signed numbers (standard 7.NS.1). If needed, review these concepts and skills prior to this lesson. 

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Anchor Problems

25-30 minutes


Problem 1

The table below shows some solution values for the equation $${{y=-3x+2}}$$.

$$x$$ $$y$$
-2 8
-1 5
0 2
1 -1


Use the values in the table to determine the slope of the line represented by $${{y=-3x+2}}$$.

Guiding Questions

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Student Response

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Problem 2

A line passes through the points $$(-1, 3)$$ and $$(5, 11)$$

a.   Find the slope of the line.

b.   Is the point $$(-4, -1)$$ on the same line as the other two points? Use slope to justify your answer. 

Guiding Questions

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Student Response

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Problem 3

Find the slope of line $$m$$ and line $$n$$, shown below. 

Guiding Questions

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Student Response

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Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


Samantha found the slope of the line that passed through the points $${(2, 6)}$$ and $${(-4, 8)}$$. Her work is shown below. 

$${{8-6\over {2-(-4)}} = {2\over 2+4 }= {2\over 6} = {1\over3}}$$

Samantha made an error in her work. Describe the error and then find the correct slope of the line through the two given points.

Student Response

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Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Challenge: Line $$k$$ has a slope of $$-\frac{1}{2}$$. It passes through the points $$(x, -2)$$ and $$(-3, \frac{1}{4})$$. Find the value of $$x$$ in the coordinate point. 

Next

Graph linear equations using slope-intercept form $${y = mx + b}$$.

Lesson 8
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Comparing Proportional Relationships

Topic B: Slope and Graphing Linear Equations

Topic C: Writing Linear Equations

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