Chapter 8: Problem 47
Write the equation of the line that satisfies the given conditions. Express final equations in standard form. \(x\) intercept of \(-3\) and slope of \(-\frac{5}{8}\)
Short Answer
Expert verified
The equation is \(5x + 8y = -15\) in standard form.
Step by step solution
01
Understand the Slope-Intercept Form
The slope-intercept form of a linear equation is \( y = mx + c \), where \( m \) is the slope and \( c \) is the y-intercept. Our slope, \( m \), is given as \(-\frac{5}{8}\).
02
Use x-intercept to find y-intercept
The x-intercept is \(-3\), meaning the point \((-3, 0)\) lies on the line. Substitute into the slope-intercept form to find the y-intercept (\(c\)). Set \( y = 0 \), \( x = -3 \), and \( m = -\frac{5}{8} \):\[ 0 = -\frac{5}{8}(-3) + c \]which simplifies to:\[ 0 = \frac{15}{8} + c \]\[ c = -\frac{15}{8} \].
03
Write the Slope-Intercept Equation
Substitute \( m = -\frac{5}{8} \) and \( c = -\frac{15}{8} \) into the slope-intercept form:\[ y = -\frac{5}{8}x - \frac{15}{8} \].
04
Convert to Standard Form
The standard form of a linear equation is \( Ax + By = C \). To convert our equation, eliminate the fractions:Multiply through by 8 to clear the denominators:\[ 8y = -5x - 15 \].Rearrange to get integer coefficients:\[ 5x + 8y = -15 \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
When we talk about the slope-intercept form, we refer to one of the most convenient ways to describe a linear equation. This form is expressed as \( y = mx + c \), where:
- \( m \) represents the slope of the line
- \( c \) is the y-intercept, the point where the line crosses the y-axis
X-Intercept
The x-intercept of a line is the point where the line crosses the x-axis. At this specific point, the value of \( y \) is zero. Knowing the x-intercept is crucial for plotting and understanding the line’s behavior.
In the given exercise, the x-intercept is \(-3\), meaning the line passes through the point \((-3, 0)\). Using this point, we can determine other characteristics of the line, such as the y-intercept, by substituting the x-value into the slope-intercept equation and solving for the y-intercept \( c \). This x-intercept also helps us visualize the line on a graph, as it provides a concrete point that the line passes through.
In the given exercise, the x-intercept is \(-3\), meaning the line passes through the point \((-3, 0)\). Using this point, we can determine other characteristics of the line, such as the y-intercept, by substituting the x-value into the slope-intercept equation and solving for the y-intercept \( c \). This x-intercept also helps us visualize the line on a graph, as it provides a concrete point that the line passes through.
Standard Form
The standard form of a linear equation is another way to express a line, written as \( Ax + By = C \). In this form:
To convert an equation from the slope-intercept form \( y = mx + c \) to standard form, follow these steps:
- \( A \), \( B \), and \( C \) are integers
- \( A \) is usually positive
To convert an equation from the slope-intercept form \( y = mx + c \) to standard form, follow these steps:
- Move all terms involving variables to one side of the equation
- Eliminate fractional coefficients by multiplying through by their denominators
- Rearrange the equation to ensure \( A \), \( B \), and \( C \) are integers
Y-Intercept
The y-intercept is the point where the line crosses the y-axis. At this particular point, the value of the variable \( x \) is zero. Understanding the y-intercept is essential for locating the line on a graph quickly.
In our problem, after using the slope and the x-intercept to calculate, we found the y-intercept \( c \) to be \(-\frac{15}{8}\). This means when \( x = 0 \), \( y = -\frac{15}{8} \). Knowing the y-intercept allows us to initiate sketching the line on a graph since it gives another direct point of reference besides the slope.
In our problem, after using the slope and the x-intercept to calculate, we found the y-intercept \( c \) to be \(-\frac{15}{8}\). This means when \( x = 0 \), \( y = -\frac{15}{8} \). Knowing the y-intercept allows us to initiate sketching the line on a graph since it gives another direct point of reference besides the slope.
- Helps determine the vertical position of the line
- Used with the slope for plotting the complete linear path