Example

Writing the Inequality y12x4y \leq \frac{1}{2}x - 4 from Its Graph

To deduce the linear inequality from a graph displaying a solid boundary line defined by the equation y=12x4y = \frac{1}{2}x - 4 and a shaded lower-right half-plane, a test point can be employed. The origin (0,0)(0, 0), situated in the unshaded upper-left region, is a straightforward point to evaluate. Because it lies outside the shaded solution set, substituting x=0x = 0 and y=0y = 0 into the intended inequality must produce a false mathematical statement. Testing the 'less than or equal to' condition gives 012(0)40 \leq \frac{1}{2}(0) - 4, which simplifies to 040 \leq -4. This condition is false, correctly indicating that the half-plane containing the origin does not satisfy the inequality. Thus, the opposite, shaded half-plane represents the true solution set. Furthermore, the solid boundary line confirms that points directly on the line are included, verifying that the graph represents the inequality y12x4y \leq \frac{1}{2}x - 4.

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Updated 2026-05-06

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