Chapter 4: Problem 2
Give the slope and the \(y\)-intercept for each equation. a. \(y=-4-3 x\) b. \(2 x+7=y\) c. \(38 x-10 y=24\)
Short Answer
Expert verified
a. Slope: -3, y-intercept: -4; b. Slope: 2, y-intercept: 7; c. Slope: 3.8, y-intercept: -2.4.
Step by step solution
01
Identify the form of the equation
Each equation needs to be in the slope-intercept form, which is \( y = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept.
02
Rearrange equation (a)
Equation (a) is given as \( y = -4 - 3x \). Rewrite it as \( y = -3x - 4 \). This is already in slope-intercept form. The slope \( m \) is \(-3\) and the y-intercept \( b \) is \(-4\).
03
Rearrange equation (b)
Equation (b) is \( 2x + 7 = y \). Rearrange it to \( y = 2x + 7 \). It is in slope-intercept form where the slope \( m \) is \( 2 \) and the y-intercept \( b \) is \( 7 \).
04
Convert equation (c) to slope-intercept form
For equation (c), \( 38x - 10y = 24 \), we first need to solve for \( y \). Start by isolating \(-10y\) on one side: \( -10y = -38x + 24 \). Divide the entire equation by \(-10\) to solve for \( y \): \( y = \frac{38}{10}x - \frac{24}{10} \). Simplify to get \( y = 3.8x - 2.4 \). Hence, the slope \( m \) is \( 3.8 \) and the y-intercept \( b \) is \(-2.4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Slope
The slope of a line in the slope-intercept form equation, represented as \( y = mx + b \), is indicated by the letter \( m \). The slope tells us how steep the line is and in which direction it goes. It captures the concept of 'rise over run', essentially showing the change in \( y \) over the change in \( x \).
To visualize this, imagine climbing a hill:
To visualize this, imagine climbing a hill:
- If the slope is positive, it’s like walking uphill. For example, in equation (b) \( y = 2x + 7 \), the slope \( m \) is 2. This tells us the line goes up 2 units on the \( y \)-axis for every unit it moves right on the \( x \)-axis.
- If the slope is negative, you are going downhill. Equation (a) \( y = -3x - 4 \) has a slope of \(-3\), indicating the line declines 3 units on \( y \) for each step right on \( x \).
- A zero slope means a flat line, with no rise or fall.
The Role of Y-Intercept
The \( y \)-intercept in the slope-intercept form \( y = mx + b \) is the constant \( b \). This point is crucial because it shows where the line crosses the \( y \)-axis. This value is important to immediately identify the starting point of the line on the graph.
In each case, this value is clear once the equation is in slope-intercept form:
In each case, this value is clear once the equation is in slope-intercept form:
- For equation (a), \( y = -3x - 4 \), the \( y \)-intercept is \(-4\). This means the line touches the \( y \)-axis at the point (0, -4).
- In equation (b), \( y = 2x + 7 \), the intercept is \( 7 \), crossing the \( y \)-axis at (0, 7).
- Looking at equation (c), \( y = 3.8x - 2.4 \), sees the line hitting the \( y \)-axis at \(-2.4\).
Rearranging Equations to Slope-Intercept Form
To find the slope and y-intercept, equations should ideally be in the \( y = mx + b \) form. This rearrangement makes the properties of the line clear and easy to identify right away.
Here’s how you do it:
Here’s how you do it:
- Equation (a): The equation \( y = -4 - 3x \) looks differently at first but can be reshuffled as \( y = -3x - 4 \). Notice that you reorder terms to match the \( mx + b \) structure.
- Equation (b): Given as \( 2x + 7 = y \), this already aligns with \( y = 2x + 7 \) where you swap sides to reveal the slope and intercept cleanly. Both sides equate already to the desired form.
- Equation (c): Transforming \( 38x - 10y = 24 \) might seem challenging. Start by isolating \(-10y\), bringing \( x \) terms across, then divide through by \(-10\) to simplify: \( y = 3.8x - 2.4 \).