## Understanding Linear Inequalities

Linear inequalities are mathematical expressions that compare two different values using inequality symbols such as ** >** (greater than),

**(less than), or a combination such as**

*<***(greater than or equal to) and**

*≥***(less than or equal to). When dealing with linear inequalities, the solutions often form a region on the coordinate plane.**

*≤*## Systems of Linear Inequalities

A system of linear inequalities involves multiple linear inequalities that are to be satisfied simultaneously. Graphically, the solution to a system of linear inequalities is the intersection of the individual solutions to each inequality. In other words, the solution region is the area on the coordinate plane that satisfies all the given inequalities in the system.

### Graphing Systems of Linear Inequalities

In order to graph a system of linear inequalities, it is essential to first graph each individual linear inequality. By identifying the overlapping areas of the individual graphs, one can determine the solution to the system. When graphing linear inequalities, it is important to distinguish between solid and dotted boundary lines, as well as shaded regions to represent the inequality.

### Example of a System of Linear Inequalities

Consider the following system of linear inequalities:

\[

\begin{align*}

2x + y &\leq 4 \\

x – y &\leq 2 \\

x &\geq 0 \\

y &\geq 0 \\

\end{align*}

\]

In this system, there are four linear inequalities that need to be graphed and solved simultaneously.

#### Graphing the First Inequality: \( 2x + y \leq 4 \)

To graph the inequality \( 2x + y \leq 4 \), first graph the boundary line \( 2x + y = 4 \). This is done by finding the x and y intercepts and drawing a straight line passing through these points. Since the inequality is less than or equal to, the boundary line should be drawn as a solid line.

Next, determine which side of the line represents the solution region. This can be done by selecting a test point such as (0,0) and substituting its coordinates into the inequality. If the inequality is true for this point, then the region containing the test point is the solution.

#### Graphing the Second Inequality: \( x – y \leq 2 \)

Similarly, graph the boundary line \( x – y = 2 \) by finding the x and y intercepts and drawing a solid line passing through these points. Again, test a point to determine which side represents the solution region.

#### Graphing the Inequalities \( x \geq 0 \) and \( y \geq 0 \)

The inequalities \( x \geq 0 \) and \( y \geq 0 \) represent the constraints that x and y must be greater than or equal to 0, which forms the first quadrant in the coordinate plane. Graph these inequalities by shading the region in the first quadrant.

#### Finding the Solution Region

By considering the shaded regions and the overlapping areas of the boundary lines, the solution to the system can be identified. The solution region will be the area that satisfies all the given inequalities in the system.

## Selecting the System of Linear Inequalities

When asked to select the system of linear inequalities whose solution is graphed, it is crucial to pay attention to the specific conditions given and accurately represent them in the system. Here are some key factors to consider when selecting the appropriate system of linear inequalities:

### Understanding the Conditions

Before selecting the system of linear inequalities, it is important to clearly understand and interpret the given conditions. These conditions often form the basis for setting up the system of linear inequalities. Identifying the key relationships and constraints within the problem will guide the selection of the appropriate inequalities.

### Translating Conditions into Inequalities

Once the conditions are understood, the next step is to translate them into mathematical inequalities. Depending on the problem, these inequalities may represent constraints, limits, or requirements that must be satisfied in order to find the solution. It is essential to accurately represent the conditions as linear inequalities.

### Formulating a Consistent System

When selecting the system of linear inequalities, it is crucial to ensure that the inequalities are consistent and form a coherent system. This means that the inequalities do not contradict each other and can be graphed together to represent a feasible solution region. Inconsistencies in the system may lead to an empty solution or an inaccurate representation of the problem.

### Consideration of Boundary Conditions

In some cases, boundary conditions such as greater than or equal to (** ≥**) and less than or equal to (

**) may be specified. It is important to accurately represent these boundary conditions in the system of linear inequalities, as they affect the graphing and interpretation of the solution region.**

*≤*## Applying the Selection Process

To illustrate the process of selecting the appropriate system of linear inequalities and graphing its solution, consider the following example:

Suppose a company produces two types of products, P1 and P2, using two machines A and B. Machine A can produce up to 100 units of P1 and 50 units of P2 per day, while machine B can produce up to 80 units of P1 and 60 units of P2 per day. The company’s production capacity is limited to 200 units of P1 and 150 units of P2 per day. Additionally, the company wants to produce at least 40 units of P1 and 30 units of P2 per day.

To formulate the system of linear inequalities and graph its solution, the following steps can be taken:

### Identifying the Variables and Constraints

In this example, the variables represent the production quantities of P1 and P2. The constraints are determined by the production capacity of machines A and B, as well as the overall production requirements of the company.

Let:

– \( x \) = units of P1

– \( y \) = units of P2

The constraints can be summarized as:

– Machine A: \( x \leq 100 \) and \( y \leq 50 \)

– Machine B: \( x \leq 80 \) and \( y \leq 60 \)

– Production capacity: \( x + y \leq 200 \)

– Minimum production: \( x \geq 40 \) and \( y \geq 30 \)

### Translating Constraints into Inequalities

The constraints identified above can be translated into the following system of linear inequalities:

\[

\begin{align*}

x &\leq 100 \\

y &\leq 50 \\

x &\leq 80 \\

y &\leq 60 \\

x + y &\leq 200 \\

x &\geq 40 \\

y &\geq 30 \\

\end{align*}

\]

This system of inequalities represents the production constraints and requirements of the company.

### Graphing the Solution Region

By graphing the system of linear inequalities on the coordinate plane, the solution region can be identified. Each inequality represents a boundary line, and the overlapping areas indicate the feasible region where all the constraints are satisfied.

After graphing the system, the solution region represents the combinations of P1 and P2 production quantities that meet the company’s requirements and constraints.

## Advantages of Graphing Systems of Linear Inequalities

The process of graphing systems of linear inequalities offers several advantages when solving real-world problems and mathematical scenarios. Some of these advantages include:

### Visual Representation

Graphing systems of linear inequalities provides a visual representation of the solution region, making it easier to understand and interpret the feasible solutions. The use of the coordinate plane and graphical representation enhances the clarity of the solution.

### Identification of Feasible Region

By graphing the system of linear inequalities, the feasible region where all the constraints are satisfied can be easily identified. This allows for a quick assessment of the valid solutions to the problem at hand.

### Comparison of Multiple Constraints

When dealing with multiple constraints and conditions, graphing systems of linear inequalities enables a comparison of the individual constraints and their combined effect on the solution region. It provides a comprehensive view of how different constraints interact with each other.

### Optimization and Decision-Making

In optimization problems, graphing systems of linear inequalities assists in making informed decisions regarding the best possible outcome within the feasible region. It allows for the identification of optimal solutions based on the objective function and the constraints.

## Conclusion

Selecting the system of linear inequalities whose solution is graphed involves careful consideration of the given conditions and constraints, translating them into mathematical inequalities, and graphing the solution region to identify the feasible outcomes. The process of graphing systems of linear inequalities offers numerous advantages, including visual representation, identification of the feasible region, comparison of multiple constraints, and support for optimization and decision-making. By understanding and applying the principles of graphing linear inequalities, individuals can effectively solve a wide range of mathematical and real-world problems.