Example

Writing the Inequality y2x1y \geq 2x - 1 from Its Graph

To determine the linear inequality for a given graph with a known boundary line, one must identify the correct inequality symbol and ascertain whether the boundary is included. Consider a graph where the boundary line is given by the equation y=2x1y = 2x - 1, drawn as a solid line, with the shaded solution region occupying the top-left half-plane. This boundary line divides the coordinate plane into two regions: one satisfying y>2x1y > 2x - 1 and the other satisfying y<2x1y < 2x - 1. To determine which mathematical condition applies to the shaded area, a convenient test point that is not on the line—such as the origin (0,0)(0, 0)—is selected. Substituting x=0x = 0 and y=0y = 0 into the inequality yields 0>2(0)10 > 2(0) - 1, which simplifies to the true statement 0>10 > -1. Because the condition holds true, the half-plane containing (0,0)(0, 0) represents the solution set for y>2x1y > 2x - 1. Furthermore, the solid boundary line visually indicates that points exactly on the line are included in the solution set, requiring the use of a non-strict inequality symbol. Combining these facts, the graph represents the complete inequality y2x1y \geq 2x - 1.

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Updated 2026-05-06

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