Chapter 1: Problem 18
Find an equation of the line described. Then sketch the line. The line with slope \(\frac{1}{2}\) and \(y\) intercept \(-1\)
Short Answer
Expert verified
The equation is \( y = \frac{1}{2}x - 1 \).
Step by step solution
01
Identify the Slope and Intercept
The slope of the line is given as \( \frac{1}{2} \), and the \( y \)-intercept is \(-1\). This information allows us to use the equation of a line in slope-intercept form.
02
Use Slope-Intercept Form
The slope-intercept form of a line is \( y = mx + b \), where \( m \) is the slope and \( b \) is the \( y \)-intercept. Here, \( m = \frac{1}{2} \) and \( b = -1 \). So, the equation becomes \( y = \frac{1}{2}x - 1 \).
03
Sketch the Line
To sketch the line, start at the \( y \)-intercept, which is \(-1\) on the \( y \)-axis. Then use the slope \( \frac{1}{2} \) to determine the next point: rise 1 unit up and run 2 units to the right. Plot this second point.
04
Draw the Line
Once you have at least two points, draw a straight line through them extending in both directions, which represents the infinite nature of a linear equation. Make sure the line crosses the \( y \)-axis at \(-1\) and follows the plotted slope.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
The slope-intercept form is a method of expressing the equation of a straight line using two main components: the slope and the y-intercept. This form is written as:
\[ y = mx + b \]
Here,
This makes it easy to define a line and is especially helpful for graphing and solving problems involving linear equations.
\[ y = mx + b \]
Here,
- \( y \) is the dependent variable (usually represented on the vertical axis of a graph).
- \( m \) represents the slope of the line.
- \( x \) is the independent variable (usually represented on the horizontal axis of a graph).
- \( b \) is the y-intercept.
This makes it easy to define a line and is especially helpful for graphing and solving problems involving linear equations.
Graphing Lines
Graphing a line involves plotting points on a coordinate plane and connecting them to form a straight line. To graph a line in slope-intercept form:
- Start by identifying the y-intercept \( b \). This point is where the line crosses the y-axis.
- Plot the y-intercept on the coordinate plane.
- Use the slope \( m \) to determine another point on the line. Remember, slope is the ratio of "rise" over "run."
- "Rise" refers to how far up or down you go from the y-intercept, and "run" refers to how far right you go.
Slope of a Line
The slope of a line measures its steepness and direction on a graph. It is represented by \( m \) in the slope-intercept form.
The slope is calculated as the ratio of the change in the y-values (rise) to the change in the x-values (run) between two points on the line:
\[ m = \frac{\Delta y}{\Delta x} = \frac{y_2-y_1}{x_2-x_1} \]
The slope is calculated as the ratio of the change in the y-values (rise) to the change in the x-values (run) between two points on the line:
\[ m = \frac{\Delta y}{\Delta x} = \frac{y_2-y_1}{x_2-x_1} \]
- A positive slope means the line rises as it moves from left to right.
- A negative slope means the line falls as it moves from left to right.
- A slope of zero indicates a horizontal line.
- An undefined slope indicates a vertical line.
y-intercept
The y-intercept of a line is the point where it crosses the y-axis. It is denoted by \( b \) in the slope-intercept form.
To find the y-intercept in the slope-intercept equation \( y = mx + b \), simply look at the value of \( b \). This is the y-coordinate of the point on the line where \( x = 0 \).
For example, in the equation \( y = \frac{1}{2}x - 1 \):
The y-intercept is helpful when graphing, as it provides a fixed starting point from which the slope can be used to locate additional points on the line.
To find the y-intercept in the slope-intercept equation \( y = mx + b \), simply look at the value of \( b \). This is the y-coordinate of the point on the line where \( x = 0 \).
For example, in the equation \( y = \frac{1}{2}x - 1 \):
- The y-intercept is \(-1\).
The y-intercept is helpful when graphing, as it provides a fixed starting point from which the slope can be used to locate additional points on the line.