Chapter 1: Problem 26
Graph each function "by hand." [Note: Even if you have a graphing calculator, it is important to be able to sketch simple curves by finding a few important points.] $$ f(x)=-3 x+5 $$
Short Answer
Expert verified
The graph is a straight line crossing the y-axis at 5 and sloping down 3 units per 1 unit right.
Step by step solution
01
Identify the Type of Function
The function given is of the form \(f(x) = mx + c\), which is a linear function. Linear functions graph as straight lines. In this case, \(m = -3\) is the slope and \(c = 5\) is the y-intercept.
02
Plot the Y-Intercept
The y-intercept of a linear function \(f(x) = mx + c\) is the point where the line crosses the y-axis. For \(f(x) = -3x + 5\), the y-intercept is \(5\). Therefore, plot the point \((0, 5)\) on the graph.
03
Use the Slope to Find Another Point
The slope \(m\) indicates the rise over run. Since \(m = -3\), it implies a rise of \(-3\) for a run of \(1\). From the y-intercept \((0, 5)\), move down 3 units and right 1 unit to locate the next point \((1, 2)\). Plot this point.
04
Draw the Line
Utilize the two points \((0, 5)\) and \((1, 2)\) to draw a straight line across the graph. This line represents the graph of the function \(f(x) = -3x + 5\).
05
Verify with Additional Points
To confirm accuracy, choose any other value for \(x\), substitute into the function, and verify the point lies on the line. For instance, for \(x = -1\), \(f(-1) = -3(-1) + 5 = 8\), so the point \((-1, 8)\) should also lie on the line.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear Equations
A linear equation is one of the simplest types of mathematical expressions, where the highest power of the variable is one. These equations are typically in the form of \( y = mx + c \), where:
- \( y \) represents the output value for each corresponding \( x \).
- \( m \) is the slope, which tells us how steep the line is.
- \( c \) stands for the y-intercept, the point where the line crosses the y-axis.
Y-Intercept
The y-intercept of a linear function is the point where the graph of the function crosses the y-axis. In terms of coordinates, this means the x-value is zero. For any linear equation in the form \( y = mx + c \), the y-intercept can be represented by the point \( (0, c) \).
For the equation \( f(x) = -3x + 5 \), the y-intercept is \(5\). This means we plot the point \( (0, 5) \) on the graph to show where the line begins its journey across the axes. Knowing the y-intercept helps plot the first crucial point, providing a foundation to graph the rest of the line.
For the equation \( f(x) = -3x + 5 \), the y-intercept is \(5\). This means we plot the point \( (0, 5) \) on the graph to show where the line begins its journey across the axes. Knowing the y-intercept helps plot the first crucial point, providing a foundation to graph the rest of the line.
Slope
The slope of a line indicates its steepness, showing how y-values change as x-values increase. It is a ratio representing 'rise over run.’ For the function \( f(x) = -3x + 5 \), our slope \( m \) is \(-3\).
- The "rise" is how much the line moves up or down vertically as you go from one point to another.
- The "run" is how far you move horizontally.
Plotting Points
Plotting points is a fundamental skill necessary for graphing linear functions. It involves identifying and marking coordinates on a graph to visualize an equation.
The process begins with determining significant points:
The process begins with determining significant points:
- Start with the y-intercept: always plot this point first as \( (0, c) \).
- Use the slope to find subsequent points, following the "rise" and "run" principle.
- Verify by placing additional points using chosen x-values and calculating the corresponding y-values.