Chapter 8: Problem 13
In Exercises \(5-20,\) graph each linear inequality. $$3 x+4 y < 2$$
Short Answer
Expert verified
Graph the boundary line, use a dashed line, and shade the region below the line where \(3x+4y < 2\).
Step by step solution
01
Express as Equation
First, we convert the inequality into an equation to find the boundary line. For the inequality \(3x + 4y < 2\), the related equation is \(3x + 4y = 2\).
02
Find Intercepts
To graph the line, find the x-intercept and y-intercept of the equation. Set \(y = 0\) to find the x-intercept: \(3x + 4(0) = 2\) gives \(x = \frac{2}{3}\). Set \(x = 0\) to find the y-intercept: \(3(0) + 4y = 2\) gives \(y = \frac{1}{2}\).
03
Draw the Boundary Line
Plot the intercepts \((\frac{2}{3}, 0)\) and \((0, \frac{1}{2})\) on the graph and draw a dashed line through these points. The line is dashed because the inequality is strictly '<' and does not include the line itself.
04
Test a Point
Select a test point not on the line to determine which side of the line to shade. A common choice is \((0,0)\). Substitute into the inequality: \(3(0) + 4(0) < 2\), which simplifies to \(0 < 2\), a true statement. Therefore, shade the region containing the origin, which is below the line.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Boundary Line
When graphing a linear inequality, the "boundary line" is a crucial concept. The boundary line represents the corresponding equation, which helps visualize where the inequality stands in relation to the coordinate plane. For the inequality \(3x + 4y < 2\), we first transform it into its related equation: \(3x + 4y = 2\). This equation represents the boundary line.
- It divides the coordinate plane into two regions.
- Once plotted, this line visually separates the true and false solutions to the inequality.
x-intercept
The x-intercept is the point where the line crosses the x-axis. For the boundary line \(3x + 4y = 2\), we find the x-intercept by setting \(y = 0\) and solving for \(x\):\[3x + 4(0) = 2\]This simplifies to \(x = \frac{2}{3}\). So, the x-intercept is \(\left( \frac{2}{3}, 0 \right)\).
- It provides a point that helps us plot the boundary line.
- Understanding intercepts is key for accurately drawing linear graphs.
y-intercept
Similar to the x-intercept, the y-intercept is where the line crosses the y-axis. For the line \(3x + 4y = 2\), find the y-intercept by setting \(x = 0\) and solving for \(y\):\[3(0) + 4y = 2\]Solving this equation gives \(y = \frac{1}{2}\), so the y-intercept is \(\left( 0, \frac{1}{2} \right)\).
- The y-intercept, along with the x-intercept, allows us to sketch the boundary line accurately.
- Mastering intercept calculations bolsters overall understanding of plotting linear graphs.
Shading Region
Shading the region is a vital step in graphing inequalities. After plotting the boundary line, we must determine which side of the line represents the solution set. With the inequality \(3x + 4y < 2\), we need to decide which area to shade.
- Select a test point not on the line, typically \((0,0)\), for ease of calculation.
- Substitute this point into the original inequality. For \(3(0) + 4(0) < 2\), the statement \(0 < 2\) holds true.