Mathematics Grade 12 15 min

Solve systems of linear inequalities by graphing

Solve systems of linear inequalities by graphing

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1

Introduction & Learning Objectives

Learning Objectives Graph a single linear inequality in two variables, correctly identifying the boundary line and shaded region. Differentiate between using a solid line (≤, ≥) and a dashed line (<, >) for the boundary. Apply the test point method to determine which half-plane to shade for an inequality. Graph a system of two or more linear inequalities on the same coordinate plane. Identify the feasible region (solution set) as the common area of intersection of all shaded half-planes. Determine the vertices of a bounded feasible region by solving systems of linear equations. Verify algebraically whether a given point is a solution to the system. How can a company determine the optimal number of products to manufacture to maximize profit while staying within budget...
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Key Concepts & Vocabulary

TermDefinitionExample Linear InequalityA mathematical statement that relates two linear expressions using an inequality symbol (<, >, ≤, ≥). It describes a region on the coordinate plane.y ≤ 2x - 1 System of Linear InequalitiesA set of two or more linear inequalities in the same variables that are considered simultaneously.{ y > x - 3, y ≤ -x + 5 } Boundary LineThe line that separates the coordinate plane into two half-planes. It is the graph of the linear equation corresponding to the inequality.For the inequality y > 3x + 2, the boundary line is y = 3x + 2. Half-PlaneThe region of the coordinate plane on one side of a boundary line. The solution to a single linear inequality is always a half-plane.For y > 3x + 2, the solution is the half-plane above the line y = 3x + 2. F...
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Core Formulas

Boundary Line Rule For inequalities with < or >, use a dashed line (---). For inequalities with ≤ or ≥, use a solid line (—). A dashed line indicates that the points on the line are NOT part of the solution. A solid line indicates that the points on the line ARE part of the solution. Test Point Method for Shading 1. Choose a test point not on the boundary line (e.g., (0,0) if possible). 2. Substitute its coordinates into the original inequality. 3. If the resulting statement is true, shade the half-plane containing the test point. 4. If it is false, shade the other half-plane. This is the most reliable method to determine which side of the boundary line represents the solutions to the inequality. Solution Identification The solution to the system of inequalities...

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Sample Practice Questions

Challenging
A company produces two products, X and Y. Each unit of X requires 2 hours of labor, and each unit of Y requires 1 hour. The company has a maximum of 80 labor hours available per day. Due to demand, it must produce at least 10 units of X. Let x be the number of units of X and y be the number of units of Y. Which system of inequalities represents these constraints?
A.2x + y ≥ 80, x ≤ 10, y ≥ 0
B.2x + y ≤ 80, x ≥ 10, y ≥ 0
C.x + 2y ≤ 80, x ≥ 10, y ≥ 0
D.2x + y ≤ 80, x ≥ 10
Challenging
Consider the system: y ≤ 5, x ≤ 6, and y ≥ -2x + k. For which value of k will the feasible region have a vertex at (6, 0)?
A.6
B.10
C.12
D.-12
Easy
When graphing the linear inequality y < 5x - 2, what type of boundary line should be used and why?
A.solid line, because the inequality includes the points on the line.
B.dashed line, because the inequality does not include the points on the line.
C.solid line, because the slope is positive.
D.dashed line, because the y-intercept is negative.

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