Chapter 1: Problem 78
For the following exercises, for each linear equation, a. give the slope \(m\) and \(y\) -intercept \(b,\) if any, and b. graph the line. $$ f(x)=-5 x+4 $$
Short Answer
Expert verified
Slope \( m = -5 \), y-intercept \( b = 4 \); graph line through (0, 4) and (1, -1).
Step by step solution
01
Identify the equation's form
The given linear equation is \( f(x) = -5x + 4 \). This is in the slope-intercept form \( y = mx + b \), where \( m \) is the slope and \( b \) is the \( y \)-intercept.
02
Extract the slope
From the equation \( f(x) = -5x + 4 \), we compare it with the slope-intercept form \( y = mx + b \). The coefficient of \( x \) is the slope \( m \). Thus, the slope \( m = -5 \).
03
Determine the y-intercept
In the equation \( f(x) = -5x + 4 \), the constant term is \( 4 \). This represents the \( y \)-intercept \( b \) when the equation is in the form \( y = mx + b \). Therefore, the \( y \)-intercept \( b = 4 \).
04
Graph the line using slope and y-intercept
Begin by plotting the \( y \)-intercept on the graph at the point \((0, 4)\). From this point, use the slope to determine another point. The slope \( m = -5 \) means rise over run is -5, or you drop 5 units for every 1 unit you move to the right. Plot another point at \((1, -1)\). Draw a line through these points to complete the graph of the equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-intercept form
In mathematics, the slope-intercept form is a way of writing the equation of a straight line. This form is essential for easily identifying and graphing linear equations. Specifically, it takes the form \( y = mx + b \), where:
- \( y \) represents the dependent variable (typically a function of \( x \))
- \( m \) stands for the slope of the line
- \( x \) is the independent variable
- \( b \) is the \( y \)-intercept, the point where the line crosses the \( y \)-axis
Graphing linear equations
Graphing linear equations involves plotting the line that represents the equation on a coordinate plane. To do this, you can start by identifying key features of the line, such as the slope and the \( y \)-intercept. Here's a step-by-step approach:
- First, ensure the equation is in slope-intercept form \( y = mx + b \).
- Locate the \( y \)-intercept, which is the point \((0, b)\), on the graph.
- Using the slope \( m \), determine the rise and run to find another point on the line. For instance, a slope of \(-5\) indicates moving down 5 units for every 1 unit you move to the right.
- Draw a straight line through these points to represent the linear equation.
Slope
The slope of a line is a crucial concept in understanding how it behaves. Represented by \( m \) in the equation \( y = mx + b \), the slope indicates the line's steepness and direction. Here's what you need to know:
- The slope represents the ratio of the vertical change (rise) to the horizontal change (run) between two points on the line.
- A positive slope suggests the line rises as you move from left to right, while a negative slope suggests it falls.
- A slope of zero indicates a horizontal line, whereas an undefined slope implies a vertical line.
y-intercept
The \( y \)-intercept is a fundamental part of a line's equation, crucial for understanding where the line starts on the \( y \)-axis. In the slope-intercept form \( y = mx + b \), \( b \) indicates the \( y \)-intercept.
- The \( y \)-intercept is the point where the line crosses the \( y \)-axis, typically at \((0, b)\).
- This base point is where \( x \) equals zero, providing a starting position for graphing the line.
- In practice, knowing the \( y \)-intercept simplifies drawing the graph as it gives a fixed initial point.