Chapter 3: Problem 62
Graph each inequality on a coordinate plane. $$ 3 x-4 y \geq 16 $$
Short Answer
Expert verified
The shaded region is above the solid line \(y = \frac{3}{4}x - 4\), as the region including and above this line represents all the points that satisfy the inequality \(3x - 4y \geq 16\).
Step by step solution
01
Rewrite the inequality in slope-intercept form
Start by isolating the variable y on one side of the inequality to convert it into the slope-intercept form, which is y = mx + b, where m is the slope and b is the y-intercept. First add 4y to both sides: \(3x \geq 4y + 16\). Then subtract 16 from both sides: \(3x - 16 \geq 4y\). Finally, divide by 4 across the inequality to solve for y: \(y \leq \frac{3}{4}x - 4\).
02
Graph the boundary line
The inequality includes the equal sign (\(\geq\)), so the boundary line will be solid. Graph the line \(\(y = \frac{3}{4}x - 4\) by first plotting the y-intercept, which is (0, -4), and then use the slope \(\)\frac{3}{4}\) to find another point. From the y-intercept, move up 3 units and right 4 units to plot the second point. Draw a solid line through these points, which is the boundary of the inequality.
03
Determine which side of the line to shade
Test a point that is not on the line to determine which half-plane to shade. A common point to use is the origin (0, 0), but since that lies on the boundary line (when y is made 0), choose a different point like (-1, 0). Substitute this point into the inequality: \(3(-1) - 4(0) \geq 16\). This simplifies to \(-3 \geq 16\), which is false. Since the point (-1, 0) does not satisfy the inequality, you shade the opposite side of the line, which is, in this case, the side that does not include the origin.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
Understanding the slope-intercept form is essential when working with linear equations and inequalities. It is expressed as \( y = mx + b \), where \( m \) represents the slope of the line, and \( b \) is the y-intercept, which is the point where the line crosses the y-axis.
To transform an inequality into this form, just like in the textbook exercise example, isolate the \( y \) variable. Here's a clearer breakdown:
To transform an inequality into this form, just like in the textbook exercise example, isolate the \( y \) variable. Here's a clearer breakdown:
- Add or subtract terms from both sides to gather the \( y \) terms on one side and the constants on the other.
- Divide by the coefficient of \( y \) to solve for \( y \).
Coordinate Plane
The coordinate plane is a two-dimensional surface formed by the intersection of two number lines: the horizontal x-axis and the vertical y-axis. Each point on the plane is represented by an ordered pair, \( (x, y) \).
Plotting a linear equation or inequality begins with identifying key points such as the y-intercept \( (0, b) \) and using the slope \( m \) to determine another point. The slope tells us how to move from one point to another on the line; a slope of \( \frac{3}{4} \) means that for every 3 units you go up (in the y-direction), you move 4 units to the right (in the x-direction).
Plotting a linear equation or inequality begins with identifying key points such as the y-intercept \( (0, b) \) and using the slope \( m \) to determine another point. The slope tells us how to move from one point to another on the line; a slope of \( \frac{3}{4} \) means that for every 3 units you go up (in the y-direction), you move 4 units to the right (in the x-direction).
Boundary Line
The boundary line in the context of graphing inequalities represents the division between the solutions that satisfy the inequality and those that do not.
Determining whether to draw a solid or dashed line is critical:
Determining whether to draw a solid or dashed line is critical:
- A solid line for the boundary is drawn when the inequality is \( \geq \) or \( \leq \), indicating that points on the line are included in the solution set.
- A dashed line is used for \( > \) or \( < \), signifying that points on the line are not part of the solution.
Shading Half-planes
After graphing the boundary line, the next step is to determine which side of the line contains the solutions to the inequality, known as shading the half-planes.
Here's a simple process for deciding where to shade:
Here's a simple process for deciding where to shade:
- Pick a test point not on the boundary line, often \( (0, 0) \) is a good choice unless it's on the line itself.
- Substitute the coordinates of the test point into the original inequality.
- If the inequality holds true, shade the side of the plane where the test point lies. If not, shade the opposite side.