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How do I know if a graph is linear or quadratic?

Differentiating between a linear and a quadratic graph is easy, look at how the graph’s information is plotted. If it follows a straight line, the graph is linear and describes the direct relationship between two variables. Quadratic equations, on the other hand, are graphed as parabolas. That is, the information will be plotted as a U-shaped curve, either ‘open’ or ‘upside-down.’

If you are creating a graph from a function and the equation contains x2, the graph is always quadratic.

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