Chapter 3: Problem 80
For exercises \(79-84\), graph the function. $$ f(x)=\frac{5}{6} x-8 $$
Short Answer
Expert verified
Graph a line through the points (0, -8) and (6, -3).
Step by step solution
01
Identify the slope and y-intercept
The given function is in the form of a linear equation, which can be written as \(f(x) = mx + b\) where \(m\) is the slope and \(b\) is the y-intercept. For the function \(f(x) = \frac{5}{6} x - 8\), the slope \(m\) is \(\frac{5}{6}\) and the y-intercept \(b\) is \(-8\).
02
Plot the y-intercept
Locate the y-intercept on the graph. The y-intercept is the point at which the line crosses the y-axis. For the function \(f(x) = \frac{5}{6} x - 8\), the y-intercept is \(-8\). Plot the point (0, -8) on the graph.
03
Use the slope to find another point
The slope \(\frac{5}{6}\) represents the rise over run, meaning for every change of 6 units in the x-direction, the y-value changes by 5 units. From the plotted y-intercept (0, -8), move 6 units to the right (positive direction on the x-axis) and 5 units up (positive direction on the y-axis) to plot the next point at (6, -3).
04
Draw the line
Using a ruler, draw a straight line through the two plotted points (0, -8) and (6, -3). This line represents the graph of the function \(f(x) = \frac{5}{6} x - 8\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope
The slope is a number that describes the steepness and direction of a line. In a linear equation written as \(f(x) = mx + b\), the slope is represented by \(m\). It tells us how much the y-value changes for a corresponding change in the x-value. In our example, the function is \(f(x) = \frac{5}{6} x - 8\), so the slope \(m\) is \(\frac{5}{6}\). This means that for every 6 units we move to the right along the x-axis, the y-value will increase by 5 units. A positive slope, like \(\frac{5}{6}\), indicates an upwards tilt from left to right. Conversely, a negative slope would mean the line tilts downwards. Understanding the slope is crucial because it defines the angle and direction of the line on the graph.
Y-Intercept
The y-intercept is the point where the line crosses the y-axis. For a linear equation like \(f(x) = mx + b\), the y-intercept is the value of \(b\). In our case, the function \(f(x) = \frac{5}{6} x - 8\) has a y-intercept of \(-8\), meaning the line crosses the y-axis at point \((0, -8)\). This point is critical for graphing because it provides a starting position from which you can use the slope to find other points on the line. To plot the y-intercept, locate \(-8\) on the y-axis and mark it with a point. It serves as a key anchor point for drawing the entire graph.
Rise over Run
The 'rise over run' is a way to describe the slope of the line. It explains how many units the line rises (or falls) vertically for every unit it runs (moves) horizontally. For the equation \(f(x) = \frac{5}{6} x - 8\), the slope \(\frac{5}{6}\) tells us that for every 6 units we move to the right along the x-axis, the line rises 5 units. You start from the y-intercept point, move horizontally 6 units, and then move vertically 5 units up. This helps in marking out another point through which the line will pass. Once you have at least two points, you can draw a straight line to represent the linear function.
Linear Equation
A linear equation forms a straight line when plotted on a graph. It can be written in the standard form \(f(x) = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. The given function \(f(x) = \frac{5}{6} x - 8\) is a linear equation with a slope of \(\frac{5}{6}\) and a y-intercept of \(-8\). To graph this linear function, you start by plotting the y-intercept (0, -8). Then, use the slope to find another point: move 6 units to the right and 5 units up from the y-intercept to reach (6, -3). Drawing a line through these points will give you the graph of the function. Linear equations are foundational in algebra and help in understanding relationships between variables.