Example

Solving {y<12x+3,  y<3x4}\{y < -\frac{1}{2}x + 3,\; y < 3x - 4\} by Graphing

Solve the system {y<12x+3y<3x4\left\{\begin{array}{l} y < -\frac{1}{2}x + 3 \\ y < 3x - 4 \end{array}\right. by graphing.

Step 1 — Graph y<12x+3y < -\frac{1}{2}x + 3. The boundary line is y=12x+3y = -\frac{1}{2}x + 3. Because the inequality uses << (strict), draw a dashed line. Test (0,0)(0, 0): 0<12(0)+30 < -\frac{1}{2}(0) + 3 gives 0<30 < 3, which is true, so shade the side that contains the origin.

Step 2 — Graph y<3x4y < 3x - 4 on the same grid. The boundary line is y=3x4y = 3x - 4. Because the inequality uses << (strict), draw a dashed line. Test (0,0)(0, 0): 0<3(0)40 < 3(0) - 4 gives 0<40 < -4, which is false, so shade the side that does not contain the origin.

Step 3 — Identify the solution. The solution is the overlapping shaded region. The intersection point of the boundary lines is not included because both lines are dashed.

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 2026-04-28

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