Chapter 2: Problem 24
Graph the solution set. $$x-3 y>0$$
Short Answer
Expert verified
Graph the line \(y = \frac{x}{3}\) as dashed and shade below it.
Step by step solution
01
Rearrange the Inequality
To graph the inequality, first rearrange it to solve for \(y\). Begin with the original inequality: \(x - 3y > 0\). To isolate \(y\), subtract \(x\) from both sides to get: \(-3y > -x\). Next, divide through by \(-3\), remembering to reverse the inequality sign when dividing by a negative number: \(y < \frac{x}{3}\).
02
Graph the Boundary Line
Graph the boundary line for the equation \(y = \frac{x}{3}\). This line has a y-intercept of 0 and a slope of \(\frac{1}{3}\). Draw this line as a dashed line because the inequality is strictly less than (<), not less than or equal to (\(\leq\)).
03
Determine the Shading Region
Since the inequality is \(y < \frac{x}{3}\), the solution set is below the line. To determine this region, pick a test point not on the line, such as (0,0). Substitute this point into the inequality: \(0 < \frac{0}{3}\), which is true. Therefore, shade the area below the dashed line as this represents the solution set.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Boundary Line
When graphing an inequality like \(x - 3y > 0\), it's important to first identify the boundary line. The boundary line represents the equation when the inequality becomes an equality, \(y = \frac{x}{3}\) in this case. This line serves as a clear marker dividing the coordinate plane into regions where the inequality holds true and where it doesn't. Here's how to handle the boundary line:
- **Identify the Type of Line**: For an inequality that uses 'greater than' (\(>\)) or 'less than' (\(<\)), the boundary line is dashed. This indicates that points on the line itself are not part of the solution set.
- **Graphing the Line**: Analyze its slope and intercept. In the line \(y = \frac{x}{3}\), the slope is \(\frac{1}{3}\), and it passes through the origin, \((0,0)\).
Shading Region
Once the boundary line for the inequality \(y < \frac{x}{3}\) is drawn, the next step is to determine which side of the line to shade. The shaded region on a graph visually represents all the solutions to the inequality.Here's a helpful approach:
- **Pick a Test Point**: Choose a point not on the boundary line, like the origin \((0, 0)\), unless the line passes through it—any other point can work in that case.
- **Substitute and Test**: Plug this point into the inequality to see if the inequality holds true. For \((0,0)\), substitute into \(0 < \frac{0}{3}\). The statement holds true, confirming that this side of the line is the solution area.
- **Shade the Region**: Since the test point satisfies the inequality, shade the entire region including it. For \(y < \frac{x}{3}\), shade below the line.
Inequality Solution Set
The inequality solution set consists of all the points on a coordinate plane that satisfy a given inequality. In the case of \(x - 3y > 0\), or equivalently \(y < \frac{x}{3}\), every point in the shaded region adheres to the inequality's condition.Key characteristics of an inequality solution set include:
- **Exclusivity of the Boundary**: Because the original inequality is strict (\(>\) or \(<\)), points on the dashed boundary line do not belong to the solution set. This distinction is crucial for determining the accuracy of the set.
- **Continuous Nature**: The solution set is often a continuous region. This means there are infinitely many solutions forming a continuous area rather than discrete points.
- **Visual Representation**: The solution set is best understood through its visual representation on a graph. Seeing the shaded region in relation to the boundary line helps one comprehend the extent and range of solutions.