Chapter 5: Problem 28
Sketch the graph of the given equation. Label the intercepts. $$3 x-7 y=21$$
Short Answer
Expert verified
The x-intercept is \((7, 0)\) and the y-intercept is \((0, -3)\).
Step by step solution
01
- Identify the equation format
The given equation is in the standard linear form: \(3x - 7y = 21\).
02
- Find the x-intercept
To find the x-intercept, set \(y = 0\) and solve for \(x\).\[3x - 7(0) = 21\]\[3x = 21\]\[x = 7\]The x-intercept is \((7, 0)\).
03
- Find the y-intercept
To find the y-intercept, set \(x = 0\) and solve for \(y\).\[3(0) - 7y = 21\]\[-7y = 21\]\[y = -3\]The y-intercept is \((0, -3)\).
04
- Plot the intercepts on the graph
Plot the points \((7, 0)\) and \((0, -3)\) on the coordinate plane. These points are the intercepts.
05
- Draw the line
Draw a straight line through the points \((7, 0)\) and \((0, -3)\). This line represents the equation \(3x - 7y = 21\).
06
- Label the intercepts
Label the points \((7, 0)\) as the x-intercept and \((0, -3)\) as the y-intercept on the graph.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
X-Intercept
To understand the x-intercept, picture the point where the line crosses the x-axis on the coordinate plane. In simpler terms, it's where the line meets the horizontal line (x-axis). At this point, the value of y is always zero.
Finding the X-Intercept
\[ 3x - 7(0) = 21 \] \[ 3x = 21 \]
\[ x = 7 \]
So, the x-intercept is \( (7, 0) \). This is the point where the line touches the x-axis.
Remember, on the graph, this is noted as (7, 0).
Finding the X-Intercept
- In any linear equation, set y = 0.
- Solve for x.
\[ 3x - 7(0) = 21 \] \[ 3x = 21 \]
\[ x = 7 \]
So, the x-intercept is \( (7, 0) \). This is the point where the line touches the x-axis.
Remember, on the graph, this is noted as (7, 0).
Y-Intercept
The y-intercept is where the line crosses the y-axis. This is the vertical line on the coordinate plane. At this point, the value of x is always zero.
Finding the Y-Intercept
\[ 3(0) - 7y = 21 \] \[ -7y = 21 \]
\[ y = -3 \]
So, the y-intercept is \( (0, -3) \). This is the point where the line touches the y-axis.
On the graph, we mark this as (0, -3).
Finding the Y-Intercept
- In any linear equation, set x = 0.
- Solve for y.
\[ 3(0) - 7y = 21 \] \[ -7y = 21 \]
\[ y = -3 \]
So, the y-intercept is \( (0, -3) \). This is the point where the line touches the y-axis.
On the graph, we mark this as (0, -3).
Coordinate Plane
The coordinate plane is a two-dimensional surface on which we can graph points, lines, and curves. It consists of two perpendicular axes: the x-axis (horizontal) and the y-axis (vertical).
Each point on the plane is defined by an ordered pair \( (x, y) \). The x value tells us how far to move horizontally, and the y value shows how far to move vertically.
Steps to Graph a Line
Each point on the plane is defined by an ordered pair \( (x, y) \). The x value tells us how far to move horizontally, and the y value shows how far to move vertically.
Steps to Graph a Line
- Identify any intercepts, such as the x-intercept and y-intercept.
- Plot these intercepts on the coordinate plane.
- Draw a straight line through these points.
Standard Form of a Linear Equation
The standard form of a linear equation is represented as
\[Ax + By = C \]
Here, A, B, and C are constants. This format is handy for quickly finding intercepts and graphing lines.
Converting to Slope-Intercept Form
Sometimes it’s easier to understand and work with the equation when it is in slope-intercept form ( \( y = mx + b \) ), where m represents the slope and b represents the y-intercept.
\[Ax + By = C \]
Here, A, B, and C are constants. This format is handy for quickly finding intercepts and graphing lines.
Converting to Slope-Intercept Form
Sometimes it’s easier to understand and work with the equation when it is in slope-intercept form ( \( y = mx + b \) ), where m represents the slope and b represents the y-intercept.
- Our example equation \(3x - 7y = 21\) can be re-arranged as:
- \[-7y = -3x + 21 \]
- \[ y = \frac{3}{7}x - 3 \]