Mississippi Math FA.F.15
The Standard
Determine the rate of change of a linear function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. (8.F.4) Use the rate of change to determine if two lines are parallel, perpendicular, or neither.
2025 Mississippi College- and Career-Readiness Standards for Mathematics
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students find a line's slope from a story, two points, a table, or a graph. They compare slopes to decide whether two lines are parallel, perpendicular, or neither.
What Mastery Looks Like
- Students calculate slope by dividing the change in y by the change in x. They know parallel lines have equal slopes and different intercepts. For perpendicular lines, they use negative reciprocal slopes, or recognize a horizontal and vertical pair.
Common Misconceptions
- Students may divide the change in x by the change in y, or subtract coordinates in different orders. Some think slopes of 2 and -2 are perpendicular. Others give a vertical line a slope of zero instead of undefined.
How to Assess It
- Exit ticket: A line passes through (1, 2) and (3, 6). Is it parallel, perpendicular, or neither to y = -1/2x + 4? Show both slopes.
Lesson moves
Ways to Teach It
Plot (1, 2) and (3, 6) on graph paper, count rise and run, then draw a perpendicular line through (1, 2).
Ask: Two tables both show y increasing by 3 when x increases by 1. Must they show the same line? Explain.
Hand out cards showing equations and tables; students sort line pairs as parallel, perpendicular, or neither and explain their choices.
Show a ramp rising 1 foot over 12 feet; students calculate its slope and sketch a parallel ramp on graph paper.
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Printable FA.F.15 Worksheet
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Related Standards
- FA.F.16
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. (8.F.4)
- FA.F.20
Compare the properties of two functions, each represented in a different way (algebraically, graphically, numerically in tables, or by verbal descriptions). For...
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