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# 2022 PA-A-2-3

last edited by 10 months ago

PA.A.2.3

PA.A.2.3 Identify graphical properties of linear functions including slope and intercepts. Know that the slope equals the rate of change, and that the y-intercept is zero when the function represents a proportional relationship.

## In a Nutshell

Extending the understanding of linear data, students will be able to determine the rate of change between two ordered pairs or models, such as graphs and tables and identify it as the slope of a line. Students will be also able to determine the y-intercept of a linear function when the x value is zero. Students will understand that the origin in a proportional relationship represents a linear function with a y-intercept of zero.

## Teacher Actions

• Develop a Deep and Conceptual Understanding when identifying properties of the slope and y-intercepts of a linear function using models, such as graphs, tables, and equations.

• Develop Ability to Make Conjectures, Model and Generalize when examining patterns of change between coordinate points, in tables and/or graphs, to draw conclusions about properties of slope for any linear function, including a negative rate of change.

• Develop Accurate and Appropriate Procedural Fluency when using efficient and accurate procedures with strategies to determine the constant of proportionality (unit rate or slope) for various mathematical situations of linear functions, including proportional relationships.

• Develop the Ability to Communicate Mathematically when translating the idea of slope to rate of change in various mathematical situations and demonstrate understanding through verbal, written, and visual explanations.
• Use and connect mathematical representations by allowing students to develop different strategies for calculating and modeling slope both graphically and mathematically.

• Pose purposeful questions that allow students to view slope in a contextual problem as a rate of change between 2 variables; instead of only a value that can be written as a fraction.

• Implement meaningful tasks that promote reasoning and problem-solving by giving students ample examples of linear equations and their graphs to explore proportional vs non-proportional relationships. Allow students to look for patterns to discover why graphs are classified as either proportional or nonproportional and determine how these patterns are connected to linear functions.

## Misconceptions

• Understand that slope is the constant rate of change between two variables and can be represented by similar triangles.

• Understand the y-intercept of a linear function is the location where the line intersects the y-axis and the x-value is zero.

• Interpret the slope, including both positive and negative rates of change, and y-intercept in the context of the given mathematical situations.

• Know a proportional relationship is a linear function that contains a y-intercept at y=0.

•  Be able to describe what makes a relationship proportional and in turn, non-proportional, and identify the properties of each representation when given the data in a table, equation, graph, or mathematical situation.

• Students confuse which value within a linear equation is the y-intercept.

• When calculating the slope from a graph, students sometimes will not pay attention to the "direction" of the rise or the run which will sometimes cause the sign of the slope to be wrong.

## Prior Knowledge

• Determine and compare the unit rates (constant of proportionality, slope, or rate of change) (7.A.2.1)

• Distinguish between proportional and non-proportional relationships (7.A.1.1)

• Recognize that the graph of a proportional relationship is a line through the origin and the coordinate (1,r), where r is the slope and the unit rate (constant of proportionality, k) (7.A.1.2)

• Analyze, use and apply mathematical models and other data sets to calculate and interpret slope and the x- and y-intercepts of a line (A1.A.4.1).

• Analyze and interpret mathematical models involving lines that are parallel, perpendicular, horizontal, and vertical (A1.A.4.2).

OKMath Framework Introduction

Pre-Algebra Introduction