Chapter 3: Problem 19
Exer. 19-20: Sketch the graphs of the lines on the same coordinate plane. $$ y=x+3, \quad y=x+1, \quad y=-x+1 $$
Short Answer
Expert verified
Plot the lines by their y-intercepts and slopes on a coordinate plane to see the graph.
Step by step solution
01
Identify the Lines
First, let's identify the equations of the lines that will be graphed:1. Line 1: \(y = x + 3\).2. Line 2: \(y = x + 1\).3. Line 3: \(y = -x + 1\).These are all linear equations in slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept.
02
Determine Key Features of Each Line
For each line, identify the slope and y-intercept:1. For \(y = x + 3\): - Slope \(m = 1\) - Y-intercept \(b = 3\)2. For \(y = x + 1\): - Slope \(m = 1\) - Y-intercept \(b = 1\)3. For \(y = -x + 1\): - Slope \(m = -1\) - Y-intercept \(b = 1\)
03
Set Up the Coordinate Plane
Prepare a coordinate plane:
- Draw a vertical axis for y and a horizontal axis for x.
- Use an appropriate scale for the axes, considering the y-intercepts and the slopes.
04
Plot the Y-Intercepts
Plot the y-intercepts of each line on the vertical axis:1. \(y = x + 3\): Point (0, 3).2. \(y = x + 1\): Point (0, 1).3. \(y = -x + 1\): Point (0, 1).
05
Use the Slope to Plot a Second Point and Draw the Lines
For each line, start from the y-intercept and use the slope to find another point:1. For \(y = x + 3\): - From (0, 3), slope 1 means rise 1 and run 1 to reach (1, 4). - Draw a line through points (0, 3) and (1, 4).2. For \(y = x + 1\): - From (0, 1), slope 1 means rise 1 and run 1 to reach (1, 2). - Draw a line through points (0, 1) and (1, 2).3. For \(y = -x + 1\): - From (0, 1), slope -1 means rise -1 and run 1 to reach (1, 0). - Draw a line through points (0, 1) and (1, 0).
06
Label Your Lines
Finally, label each line on your graph to distinguish them:- Label the line through (0, 3) and (1, 4) as \(y = x + 3\).- Label the line through (0, 1) and (1, 2) as \(y = x + 1\).- Label the line through (0, 1) and (1, 0) as \(y = -x + 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
The slope-intercept form of a linear equation is a way of expressing the equation of a line. This form is given by the central formula: \[ y = mx + b \]where:
- \(m\) is the slope of the line.
- \(b\) is the y-intercept, which is where the line crosses the y-axis.
Coordinate Plane
The coordinate plane is a two-dimensional surface where we can graph equations and visualize the relationships between variables. It consists of:
- A horizontal number line, called the x-axis.
- A vertical number line, called the y-axis.
- The x-axis represents the input or independent variable.
- The y-axis represents the output or dependent variable.
Slope and Y-Intercept
The slope and y-intercept are key features of a line, defining its direction and position on the plane.
- Slope \(m\): This is a measure of the line's steepness and direction. It is calculated by \(\text{slope} = \frac{\text{rise}}{\text{run}}\). This ratio shows how much the line goes up or down (rise) for each step it moves horizontally (run).Positive slope: The line rises as you move right.
Negative slope: The line falls as you move right. - Y-Intercept \(b\): This is the value of \(y\) when \(x=0\). It is the point where the line crosses the y-axis. It offers a clear starting point for drawing the line.
Plotting Points
Plotting points on the coordinate plane is the fundamental step in graphing linear equations. Here's how to plot points easily:To graph a line, such as those given by an equation in slope-intercept form:
- Start by identifying your y-intercept \((0, b)\) and place a point there on the y-axis.
- Use the slope \(m\), often as a fraction \(\frac{rise}{run}\), to find another point. From the y-intercept, move up or down (rise) and then right (run). Example: For a slope of \(2\), move up 2 and right 1, reaching the new point.