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Chapter 8: Problem 10
Sketch the graph of the solution set to each linear inequality in therectangular coordinate system. $$x-2 y \geq 6$$
Short Answer
Expert verified
Plot the boundary line for \( x - 2y = 6 \). Shade the region above the line.
Step by step solution
01
- Rewrite the Inequality as an Equation
Rewrite the given inequality as an equation to identify the boundary line. The given inequality is \[ x - 2y \geq 6 \] Rewrite this as an equation: \[ x - 2y = 6 \]
02
- Find the x- and y-Intercepts
To find the x-intercept, set y to 0 and solve for x. \[ x - 2(0) = 6 \] \[ x = 6 \]The x-intercept is (6, 0).To find the y-intercept, set x to 0 and solve for y. \[ 0 - 2y = 6 \] \[ -2y = 6 \] \[ y = -3 \]The y-intercept is (0, -3).
03
- Draw the Boundary Line
Plot the intercepts (6, 0) and (0, -3) on the graph. Draw a straight line through these points. Because the inequality is \( \geq \), the boundary line will be a solid line, indicating that points on the line are included in the solution set.
04
- Determine the Shading Area
Choose a test point not on the boundary line to determine which side to shade. The origin \((0, 0)\) is usually a convenient test point. Substitute \((0, 0)\) into the original inequality: \[ 0 - 2(0) \geq 6 \] \[ 0 \geq 6 \]This is false, so the side of the line that does not contain the origin will be shaded.
05
- Finalize the Graph
Shade the region of the graph that is on the opposite side of the test point in relation to the boundary line. This shaded area represents the solution set for the inequality \( x-2y \geq 6 \).
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Boundary Line
When graphing a linear inequality, the first step is to rewrite the inequality as an equation to find the boundary line.
In our example, we start with the inequality: \(x - 2y \geq 6\).
We rewrite this as the equation: \[ x - 2y = 6 \].
The boundary line helps us visually separate the coordinate plane into different regions where the inequality may or may not hold.
Since the inequality symbol is greater than or equal to (\( \geq \)), it means that the points on the boundary line itself are also solutions.
We depict this with a solid line.
A dashed line would be used if the inequality was strictly greater than (\(>\)) or strictly less than (\(<\)).
Intercepts
Finding the intercepts of the boundary line is crucial for plotting it.
These are the points where the line crosses the x-axis and y-axis. In our example, we solve for the intercepts as follows:
- x-intercept: Set y to 0 and solve for x:
- y-intercept: Set x to 0 and solve for y:
\[ x - 2(0) = 6 \]
\[ x = 6 \]
Thus, the x-intercept is (6, 0).
\[ 0 - 2y = 6 \]
\[ -2y = 6 \]
\[ y = -3 \]
So, the y-intercept is (0, -3).
These intercepts provide specific points to plot the boundary line accurately on the graph.
Shading Regions
The shaded region on the graph represents all the solutions to the inequality.
After plotting the boundary line using the intercepts, you need to determine which side of the line contains the solutions.
Choose a test point that is not on the boundary line, like the origin (0, 0), to test the inequality.
In our example, substituting (0, 0) into \[ x - 2y \geq 6 \]:
\[ 0 - 2(0) \geq 6 \]
Simplifies to \[ 0 \geq 6 \], which is false.
Therefore, the region that does not contain the point (0, 0) is the solution region.
This region should be shaded to indicate all possible solutions to the inequality.
Solution Set
The solution set of the inequality is all the points (x, y) in the shaded region and on the boundary line.
These points satisfy the inequality \[ x - 2y \geq 6 \].
The shading gives a visual representation of the range of solution possibilities.
It includes every point below and to the right of the solid boundary line, confirming that all these points make the inequality true.
This set helps us understand and confirm our solutions visually.
By accurately drawing and shading the graph, we ensure that we capture all potential solutions to the given linear inequality.
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