Chapter 5: Problem 25
Find the slope and the \(y\) -intercept of the line with the given equation and sketch the graph using the slope and the \(y\) -intercept. A calculator can be used to check your graph. $$5 x-2 y=40$$
Short Answer
Expert verified
The slope is \(\frac{5}{2}\) and the \(y\)-intercept is \(-20\).
Step by step solution
01
Rewrite to Slope-Intercept Form
The standard form of the line is given as \(5x - 2y = 40\). Our first task is to rewrite it in the slope-intercept form, which is \(y = mx + b\), where \(m\) is the slope and \(b\) is the \(y\)-intercept. Solve for \(y\) by isolating it on one side of the equation: Start with the equation: \[5x - 2y = 40\]Subtract \(5x\) from both sides: \[-2y = -5x + 40\]Divide each term by \(-2\) to solve for \(y\): \[y = \frac{5}{2}x - 20\]Now, the equation is in the form \(y = mx + b\) with \(m = \frac{5}{2}\) and \(b = -20\).
02
Identify Slope and y-intercept
Using the equation \(y = \frac{5}{2}x - 20\), identify the slope \(m\) and the \(y\)-intercept \(b\). The slope \(m\) is the coefficient of \(x\), which is \(\frac{5}{2}\). The \(y\)-intercept \(b\) is the constant term, which is \(-20\).
03
Plot the y-intercept
On a Cartesian plane, start by plotting the \(y\)-intercept. This is the point where the line crosses the \(y\)-axis. Given \(b = -20\), locate the point \((0, -20)\) on the graph.
04
Use Slope to Find Another Point
The slope \(m = \frac{5}{2}\) means that for every increase of 2 units in \(x\), \(y\) increases by 5 units. Start from the \(y\)-intercept \((0, -20)\) and move 2 units to the right (to \(x = 2\)) and 5 units up (to \(y = -15\)). Plot the second point \((2, -15)\).
05
Draw the Line
With the two points \((0, -20)\) and \((2, -15)\) plotted, draw a straight line through these points. This line represents the graph of the equation \(5x - 2y = 40\).
06
Verify with a Calculator
Optionally, use a graphing calculator to confirm the graph by inputting the equation \(y = \frac{5}{2}x - 20\). Ensure that the slope appears consistent and that the line correctly crosses the \(y\)-axis at \(-20\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear Equations
Linear equations represent relationships between two variables, usually in the form of a straight line when graphed. These equations have a standard form: \(Ax + By = C\). In this standard form, \(A\), \(B\), and \(C\) are constants. The equation given in the original exercise is an example of such a form: \(5x - 2y = 40\).
To analyze it easily, you can rewrite it into the slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. This form makes it simpler to understand how the line behaves on a graph. The slope shows how much \(y\) changes with \(x\), and the y-intercept tells you the starting point on the y-axis.
Here’s why this is useful:
To analyze it easily, you can rewrite it into the slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. This form makes it simpler to understand how the line behaves on a graph. The slope shows how much \(y\) changes with \(x\), and the y-intercept tells you the starting point on the y-axis.
Here’s why this is useful:
- It's simple to identify the slope and y-intercept.
- Easy to interpret the graph’s line.
- Makes solving for one variable straightforward.
Graphing Lines
Graphing lines from a linear equation is a step-by-step process. Once the equation is in the slope-intercept form \(y = mx + b\), you can graph it using these steps:
- Start by identifying the y-intercept \(b\). This is where the line will cross the y-axis. For our exercise, \(b\) is \(-20\), so you plot the point \((0, -20)\).
- The slope \(m\) tells you the angle of the line. In this exercise, it is \(\frac{5}{2}\), meaning for every 2 units you move horizontally, you move 5 units vertically. This rise-over-run relationship helps you find another point on the line.
- After plotting the y-intercept, use the slope to find another point by moving 2 units right and 5 units up from \((0, -20)\) to get \((2, -15)\).
- Draw a straight line through both points to complete the graph.
Mathematical Solutions
Solving linear equations and understanding graphs involves finding precise mathematical solutions. Here are the steps demonstrated in the solution:
- Convert the equation into a workable form, such as slope-intercept, for clarity and ease of graphing.
- Identify the key elements like slope and intercept that allow for practical graphing and understanding of linear relationships.
- Verify your graph manually, or optionally, with a calculator, to ensure accuracy.