Maryland Math 8.AT.D.9.a
The Standard
- 8.AT.D.9
- Interpret the graph of a linear function in the form y = mx + b
Given the graph of a linear function, identify the slope and y-intercept.
Maryland College and Career Ready Standards for Mathematics (2025) · MODEL WITH FUNCTIONS.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students read the y-intercept where a line crosses the vertical axis. They find the slope by comparing the vertical and horizontal changes between two points on the line.
What Mastery Looks Like
- A student marks two points on the graph and divides the change in y by the change in x. They give the correct sign for the slope and identify the y-intercept as a value, not just a point.
Common Misconceptions
- Students may report the x-intercept instead of the y-intercept. They may divide run by rise, ignore the axis scale, or give a falling line a positive slope.
How to Assess It
- Display a graph with a line through (0, 3) and (2, -1). Ask students to mark their rise and run, then write the slope and y-intercept.
Lesson moves
Ways to Teach It
Give pairs a printed line graph and colored pencils; have them draw a slope triangle and circle the y-intercept.
Show a line through (0, 2) and (3, 5); ask, "Why is 2 the y-intercept, not 5?"
Play a card match with line graphs, slope cards, and y-intercept cards; partners explain each match.
Show a taxi fare graph through (0, 4) and (3, 10); ask what its slope and y-intercept mean in dollars.
Keep exploring
Related Standards
- 8.AT.D.9
Interpret the graph of a linear function in the form y = mx + b
- 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...
- 8.AT.D.9.b
Match a linear equation in the form y = mx + b to its graph.
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