Maryland Math 8.AT.D.9

8.AT.D.9 is a cluster heading. These are the individual standards under it.

• 8.AT.D.9.a

  Given the graph of a linear function, identify the slope and y-intercept.

• 8.AT.D.9.b

  Match a linear equation in the form y = mx + b to its graph.

01

What Students Need to Do

Students find where a line crosses the y-axis and how much y changes as x changes. They use those values to match a graph to an equation in y = mx + b form.

02

What Mastery Looks Like

A student uses two points on the line to calculate rise over run. They identify the y-intercept and choose the matching equation, even when two choices have the same intercept.

03

Common Misconceptions

Students may mistake the x-intercept for b or divide run by rise. They may give a falling line a positive slope or check only the intercept when matching an equation.

04

How to Assess It

Draw a line through (0, 3) and (2, -1). Ask students to find its slope and y-intercept, then choose from y = -2x + 3, y = 2x + 3, and y = -2x - 3.

1. 01

   Give pairs a printed line graph and colored pencils; have them mark the y-intercept and draw a slope triangle between grid points.

2. 02

   Show two lines with the same y-intercept but different slopes; ask, 'How can you tell which equation matches each line?'

3. 03

   Post four graph cards and four equation cards; have pairs match them by checking both the y-intercept and rise over run.

4. 04

   Give students a graph of a taxi fare that starts at $4 and rises $2 per mile; have them write its equation.

• 8.DS.B.4

  Use a provided linear model to make predictions based on bivariate measurement data. Interpret the meaning of the slope and y-intercept in context.

• 8.AT.A.2.b

  Use this relationship to write equations of lines in the form y = mx for lines that pass through the origin, and in the form y = mx + b for lines that include a...