Example

Writing the Inequality 3xy63x - y \geq 6 from Its Graph

When deducing the linear inequality from a graph with the boundary line 3xy=63x - y = 6, one must inspect the line style and the location of the shaded region. The graph displays a solid boundary line, meaning the inequality must include an equal sign, taking the form of \leq or \geq. To decide which symbol is correct, test a point such as the origin (0,0)(0, 0). If the origin is located in the unshaded section of the coordinate plane, substituting x=0x = 0 and y=0y = 0 into the expression 3xy3x - y must result in a false statement. The evaluation 3(0)03(0) - 0 gives 00. Because the unshaded region must yield a false statement for the correct inequality, and 060 \geq 6 is false, the inequality describing the shaded solution region is 3xy63x - y \geq 6.

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Updated 2026-05-06

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