Khan Academy
Linear and Nonlinear Functions
Decide whether a relationship can be written as a linear equation.
Watch on YouTubeTell straight-line functions apart from curved ones.
Read this first — it covers the idea in plain language with a worked example.
A linear function graphs as a straight line and can be written as y = mx + b. In a table, the output changes by a constant amount each step.
Anything that is not a straight line is nonlinear — for example y = x². In a table, the change between outputs is not constant.
Quick check
If you can write the rule as y = mx + b (no exponents on x, no x in a denominator), it is linear.
A short video that walks through this topic.
Decide whether a relationship can be written as a linear equation.
Watch on YouTubeTry a worksheet or work through some problems before the quiz.
A couple of questions to make sure this topic stuck. Retake as many times as you want.
Linear & Nonlinear Functions
Which equation represents a linear function?