Question

Graph the system of linear inequalities. \(x-3 y \geq 12\) \(x-6 y \leq 12\)

Short answer

The graph of this system of inequalities consists of two half-planes whose intersection shows the solution region. The boundaries of this region are the lines y = (x - 12)/3 and y = (x - 12)/6.

Step-by-step solution

Graph the lines

First, start by graphing each inequality as if it were an equation by replacing the inequality sign with an equals sign i.e., plot \(x - 3y = 12\) by rearranging it as \(y = (x - 12)/3\), and \(x - 6y = 12\) by rearranging it as \(y = (x - 12)/6\). These lines will be the boundaries of the solution regions of their respective inequalities.

Determine the solution regions

To figure out which side of the line satisfies each inequality, pick a test point not on the line (the point (0,0) is often a convenient choice) and plug it into the inequality. If the inequality is satisfied, shade the side of the line that includes the test point; if it's not, shade the other side. Do this for both inequalities.

Find the intersection of the solution regions

The solution to the system of inequalities is the region where the shaded areas of both inequalities overlap. This is because a point must satisfy both inequalities to satisfy the system of inequalities.

Key concepts

Linear Inequalities

Understanding linear inequalities is key to grasping the fundamental concepts of algebra. Unlike linear equations, which represent a line with a single solution, a linear inequality describes a relationship in which one side may not be exactly equal to the other, resulting in a range of solutions. For instance, the inequality

\( x - 3y \geq 12 \)

indicates that the value of \( x - 3y \) is greater than or equal to 12. We look at this inequality like a balance scale, where one side must either outweigh or be equal to the other. The inequality symbol can be less than (\( < \)), greater than (\( > \)), less than or equal to (\( \leq \)), or greater than or equal to (\( \geq \)). When we graph these inequalities, rather than drawing a line (as we would for an equation), we shade a region of the graph that represents all possible solutions that satisfy the inequality. This visual representation helps us see not just one answer, but a continuum of possibilities.

Solution Regions

Solution regions are where the magic of linear inequalities comes to life on a graph. They represent the entire set of possible solutions that satisfy a given inequality. When we graph an inequality, the line itself (also known as a boundary line) splits the graph into two halves.

For example, when we graph

\( x - 3y = 12 \)

as a part of our inequality \( x - 3y \geq 12 \) we're finding the boundary between two distinct regions. One side will include all the points where \( x - 3y \) is greater than 12, and the other will have points where it is less. The side that makes our inequality true is our solution region. It's typically marked by a shaded area on the graph. This visual tool is powerful—it helps us instantly grasp which points (or pairs of \( x \) and \( y \) values) solve the inequality, simply by seeing if they fall within the shaded zone.

Inequality Graphing

Inequality graphing is a step-by-step process that brings together the concepts of linear inequalities and solution regions. Let's break down the procedure to make it even more comprehensive. Starting with the given linear inequalities:

\(x-3y \geq 12\) and \(x-6y \leq 12\)

the first clue we get is the inequality symbol, which guides us in determining the solution region.

Step 1: Graphing the Boundary Lines

The boundary lines are graphed by treating the inequalities as equalities. This gives us two lines on the graph that divide it into halves. They show us the threshold between which points are potential solutions and which are not.

Step 2: Testing for Solutions

There's an elegant simplicity in using a test point to check which side of the boundary line is part of the solution set. If the point satisfies the inequality, we know that the entire region on that side does, too. Shading these regions on the graph visually confirms the solutions for us.

Step 3: Intersecting Solution Regions

Finally, in a system with more than one inequality, we look for where the shaded regions intersect. This overlapped area marks the set of points that satisfy all the inequalities in the system, providing us with the ultimate solution region.