Quandaries and Queries


When graphing a linear inequality, how do you know if the inequality represents the area above the line?


Hi Gina,

First plot the line and then choose some point P that is not on the line. Substitute the coordinates of the point P into the inequality. If the inequality is true for the coordinates of this point then the inequality is true for all points on the same side of the line as P. If the inequality is not true for the coordinates of P then you want all the points that are on the opposite side of the line from P.

When choosing P use a point that has easy coordinated to work with, for example (0,0) or (0,1) or (1,0).

There is a more detailed explanation in the answer to a previous question.



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