Chapter 1: Problem 19
Find an equation of the given line. Slope is \(-2 ; x\) -intercept is \(-2\).
Short Answer
Expert verified
The equation of the line is y = -2x - 4.
Step by step solution
01
Understand the given parameters
The problem provides two pieces of information: the slope of the line, which is -2, and the x-intercept, which is the point where the line crosses the x-axis, given as -2.
02
Use the slope-intercept form of a line
The slope-intercept form of a line is given by the equation y = mx + b, where m is the slope and b is the y-intercept. In this problem, we must find y-intercept (b) using the given x-intercept.
03
Determine the y-intercept (b)
Since the line crosses the x-axis at the x-intercept, the coordinates of this point can be written as (-2, 0). Substitute this point and the slope into the slope-intercept form of the line: 0 = (-2)(-2) + b.
04
Solve for b
Calculate as follows: 0 = 4 + b So, b = -4.
05
Write the final equation of the line
Substitute the value of the slope (-2) and y-intercept (-4) back into the slope-intercept form of the equation: y = -2x - 4.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
slope-intercept form
Let's start by understanding the slope-intercept form of a line, which is fundamental for finding the equation of a line. The slope-intercept form of a line is given by:
\( y = mx + b \).
This form is especially useful because it directly shows the slope and y-intercept of the line, making it easier to graph.
In the equation, the term \( m \) represents the slope of the line.
- This indicates how steep the line is and in which direction it slants.
Meanwhile, the term \( b \) represents the y-intercept.
- This is the point where the line crosses the y-axis.
So, if you know both the slope and the y-intercept, you can easily write the equation of a line in slope-intercept form, making it a critical concept to master.
slope
The slope is a measure of how steep a line is and the direction it goes.
In our problem, the slope is given as \( -2 \).
- If the slope is positive, the line rises as it moves from left to right.
- If the slope is negative, the line falls as it moves from left to right.
To calculate the slope, we use the formula: \(\frac{y_2 - y_1}{x_2 - x_1}\).
So, why is knowing the slope important?
- It allows you to understand the rate of change between the two variables in the equation.
- It also helps you determine the steepness and direction of the line.
intercept
In this exercise, the intercepts play a significant role as they help in determining the exact position of the line on a graph.
There are two types of intercepts:
- The y-intercept, which we denote as \( b \), is where the line crosses the y-axis.
The y-intercept is essential because it acts as a starting point when graphing the line, and shows the value of the function when \( x \) is 0.
The exercise gives us the x-intercept as \( -2 \), which is the point where the line crosses the x-axis.
Given this x-intercept and the slope, we can find the y-intercept by using the slope-intercept form of a line and substituting the known values into it.
This step-by-step approach makes it easier to visualize and understand the line's position and trajectory on the graph.