Chapter 2: Problem 120
For the following exercises, sketch the graph of each equation. $$f(x)=-2 x-1$$
Short Answer
Expert verified
Sketch the line passing through points (0, -1) and (1, -3) with slope -2.
Step by step solution
01
Understand the Equation Form
The equation given is a linear equation in the slope-intercept form: \( f(x) = -2x - 1 \). Here, \(-2\) is the slope (m) and \(-1\) is the y-intercept (b). This means the graph is a straight line.
02
Identify the Y-Intercept
The y-intercept of the line is the point where the line crosses the y-axis. From the equation \( f(x) = -2x - 1 \), the y-intercept is \(-1\). Thus, the line passes through the point \((0, -1)\). Plot this point on the graph.
03
Use the Slope to Find Another Point
The slope of \(-2\) means that for every 1 unit increase in \(x\), \(f(x)\) decreases by 2 units. Starting from the y-intercept \((0, -1)\), move 1 unit to the right (to \(x=1\)) and 2 units down to \(f(x)=-3\). This gives the next point \((1, -3)\). Plot this point.
04
Draw the Line
Use a ruler to draw a straight line through the points \((0, -1)\) and \((1, -3)\). Extend the line in both directions, adding arrows on either end to indicate it continues infinitely. This line represents the graph of \(f(x) = -2x - 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing functions
Graphing a function is like painting a picture on a sheet of paper. You're essentially turning the equation into a visual image. The equation we have is in the form of a linear function, which means that its graph will be a straight line. When graphing any function, you first need to identify key information, such as the slope and y-intercept. Once you gather this information, you can start plotting the function.
Here's a simple plan to graph functions effectively:
Here's a simple plan to graph functions effectively:
- Identify the type of equation: Is it linear, quadratic, or another form?
- Find the y-intercept: This is where you'll start on the graph.
- Next, use the slope to determine the direction and steepness of the line.
- Plot another point using the slope, then draw a line through your plotted points.
- Ensure the graph is extended using arrows to show it continues indefinitely.
Slope-intercept form
The slope-intercept form is a straightforward way to express a line's equation. It is written as \( y = mx + b \), where:
The slope \( m \) reflects the change in the y-coordinate (vertical change) over the change in the x-coordinate (horizontal change). If \( m = -2 \), it means that for each step to the right, you move 2 steps down. This helps in plotting additional points on the line.
This form is user-friendly because you can immediately see the slope and y-intercept, making it easy to graph or analyze the line without additional calculation.
- \( m \) is the slope, showing how steep the line is.
- \( b \) is the y-intercept, indicating where the line crosses the y-axis.
The slope \( m \) reflects the change in the y-coordinate (vertical change) over the change in the x-coordinate (horizontal change). If \( m = -2 \), it means that for each step to the right, you move 2 steps down. This helps in plotting additional points on the line.
This form is user-friendly because you can immediately see the slope and y-intercept, making it easy to graph or analyze the line without additional calculation.
Y-intercept
The y-intercept is a crucial point in graphing a line because it marks where the line intersects the y-axis. In our equation \( f(x) = -2x - 1 \), the y-intercept is \(-1\). This means when the x-value is 0, the y-value is -1, giving you the point \((0, -1)\) on the graph.
Understanding the y-intercept helps in establishing a starting point for drawing the line on the graph. By knowing where the line crosses the y-axis, you can accurately represent the function on a coordinate plane.
Understanding the y-intercept helps in establishing a starting point for drawing the line on the graph. By knowing where the line crosses the y-axis, you can accurately represent the function on a coordinate plane.
- First, plot the y-intercept on the y-axis.
- This provides a reference point for further plotting using the slope.