8.F.A.3: Linear vs. nonlinear

Also written as 8.F.3

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.

In plain words: Students read y = mx + b as a linear function whose graph is a straight line, and give examples of functions that are not linear, like A = s².

Quick picks

GoblinsExample problem
Could the table of (x, y) pairs have been generated by a linear function?

xy
01
12
24
38
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Common mistake
Calling a function linear because it keeps rising: for x = 1, 2, 3, 4, y = x² gives 1, 4, 9, 16, which rise by 3, 5, 7, so its graph is not a line.
Example Problems
Graph:
Graph:
Graph:
Khan Academy Resources
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