Example

Solving {x+y≤2,;y≥23x−1}\{x + y \leq 2,; y \geq \frac{2}{3}x - 1\} by Graphing

Solve the system {x+y≤2y≥23x−1\left\{\begin{array}{l} x + y \leq 2 y \geq \frac{2}{3}x - 1 \end{array}\right. by graphing.

Step 1 — Graph x+y≤2x + y \leq 2. The boundary line is x+y=2x + y = 2. Because the inequality uses ≤\leq (non-strict), draw a solid line. Test (0, 0): 0+0≤20 + 0 \leq 2 gives 0≤20 \leq 2, which is true, so shade the side that contains the origin.

Step 2 — Graph y≥23x−1y \geq \frac{2}{3}x - 1 on the same grid. The boundary line is y=23x−1y = \frac{2}{3}x - 1. Because the inequality uses ≥\geq (non-strict), draw a solid line. Test (0, 0): 0≥23(0)−10 \geq \frac{2}{3}(0) - 1 gives 0≥−10 \geq -1, which is true, so shade the side that contains the origin.

Step 3 — Identify the solution. The solution is the overlapping shaded region. The intersection point of the boundary lines is included in the solution because both boundary lines are solid.

Step 4 — Verify with a test point. Choose a test point in the overlapping region and substitute it into both inequalities to confirm both are true.

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Updated 2026-06-03

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