Chapter 3: Problem 6
Graph the given functions. $$y=-2 x$$
Short Answer
Expert verified
The equation \(y=-2x\) is a line through the origin with a slope of -2.
Step by step solution
01
Understanding the Slope-Intercept Form
The given function is in slope-intercept form, which is generally written as \(y = mx + b\). In this form, \(m\) represents the slope of the line, and \(b\) is the y-intercept. For the function \(y = -2x\), \(m = -2\) and \(b = 0\). This means that the line will cross the origin \((0, 0)\) and have a slope of -2.
02
Plotting the Y-intercept
The y-intercept \(b = 0\) tells us that the line crosses the y-axis at the origin. So, the first point to plot on the graph is \((0, 0)\).
03
Using the Slope to Find Another Point
The slope \(m = -2\) can be interpreted as 'rise over run.' A slope of -2 means that for every unit you move to the right (along the x-axis), you move down 2 units. Start from the y-intercept \((0,0)\), move one unit to the right to \(x = 1\), and then move two units down to \(y = -2\). Plot this point at \((1, -2)\).
04
Drawing the Line
Now that you have two points, \((0,0)\) and \((1,-2)\), you can draw a straight line through these points. This line represents the graph of the function \(y = -2x\).
05
Verifying with Additional Points
To ensure accuracy, try finding a third point. Start again from \((0,0)\), move another unit right to \(x = 2\), and 2 more units down to \(y = -4\). Plot \((2, -4)\) and check consistency with your line.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Slope-Intercept Form
The slope-intercept form of a linear equation is a straightforward way to represent a line on a graph. It's expressed as \( y = mx + b \), where:
since there is no vertical shift, then proceeds downwards to the right as determined by the slope.
- \( m \) is the slope of the line, indicating its steepness.
- \( b \) is the y-intercept, the point where the line crosses the y-axis.
since there is no vertical shift, then proceeds downwards to the right as determined by the slope.
Plotting Points Using the Equation
Graphing a linear function involves plotting key points on the coordinate plane that lies on the line. To begin, use the y-intercept from the function, which is the first point:
Begin plotting with the y-intercept because it simplifies aligning subsequent points using the slope.
- For \( y = -2x \), the y-intercept \( b = 0 \) means the line crosses the y-axis at \( (0, 0) \).
Begin plotting with the y-intercept because it simplifies aligning subsequent points using the slope.
Determining the Slope of a Line
The slope is crucial in defining how steep or flat a line is. Represented by \( m \) in the slope-intercept form, it acts as a measure of the line's "rise over run." Simply put:
Starting from the y-intercept \( (0, 0) \), if you move 1 unit to the right (\( x = 1 \)), you simultaneously move 2 units down, putting you at \( (1, -2) \). Plotting a few more points using this pattern ensures accuracy in the visualization.
- The "rise" refers to the change in y-values (vertical movement).
- The "run" refers to the change in x-values (horizontal movement).
Starting from the y-intercept \( (0, 0) \), if you move 1 unit to the right (\( x = 1 \)), you simultaneously move 2 units down, putting you at \( (1, -2) \). Plotting a few more points using this pattern ensures accuracy in the visualization.
The Role of the Y-Intercept
The y-intercept is a significant starting point for any linear graph. Defined as \( b \) in the equation \( y = mx + b \), it is the point where the line crosses the y-axis:
This consistent approach makes it easier to verify the accuracy of the plotted slope visually.
- In our example, \( b = 0 \) indicates the line passes through the origin \( (0, 0) \).
This consistent approach makes it easier to verify the accuracy of the plotted slope visually.