# Ch 3: Interpret Linear Functions: CCSS.Math.Content.8.F.A.3

Standard: Interpret the equation y = mx + b as defining a linear function, whose graph is a straight line; give examples of functions that are not linear. For example, the function A = s2, giving the area of a square as a function of its side length, is not linear because its graph contains the points (1,1), (2,4) and (3,9), which are not on a straight line.

Students who have gained proficiency in this standard are able to decide whether functions are linear, in addition to determining if they are increasing, decreasing, negative or positive. They can also find and apply the slopes and intercepts of lines.

Lessons in this standard cover concepts such as:

• Understanding the differences between nonlinear and linear functions
• Strategies for finding and applying the slopes of lines
• Tips for locating and using the intercepts of lines

Students demonstrate mastery of this standard when they can identify the traits of functions. They are also able to use the slope formula and the slope-intercept form to work with the slopes of lines. Mastery of this standard supports their college and career readiness because being able to interpret linear functions indicates preparedness for working with upper tier math concepts and helps students exercise their higher level thinking skills.

### How to Use These Lessons in Your Classroom

Here are some tips for using these lessons to support instruction in the CCSS.Math.Content.8.F.A.3 standard:

#### Comparing and Identifying Functions Lessons

View the video lesson pertaining to the identification traits of functions. Discuss. Divide the class into six sections, each assigned to linear, nonlinear, increasing, decreasing, positive or negative. Within their groups, students will design an introduction 'speech' telling about their assigned identifying traits.

#### Finding and Applying the Slope of a Line Lessons

Challenge your students to complete the quiz before viewing this video. Share the lesson with your class. Upon completion, review the practice sections for using points and equations. Divide students into small groups, assigning practice exercises to each. After checking for accuracy, ask one student from each group to teach their problem with solution to the class.

#### Finding and Applying the Intercepts of a Line Lessons

Review x- and y-intercepts and the practice problems after viewing the video lesson. Ask students to write down on a slip of paper what they find to be the most challenging aspect of this lesson. After reflection, address those issues in a future class discussion to meet the students' learning needs.

4 Lessons in Chapter 3: Interpret Linear Functions: CCSS.Math.Content.8.F.A.3
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