Chapter 9: Problem 12
In Exercises \(7-24,\) find the general form of the equation of the line satisfying the conditions given and graph the line. Through \((-7,1)\) and \((3,-5)\)
Short Answer
Expert verified
The general form of the equation is \( 3x + 5y + 16 = 0 \).
Step by step solution
01
- Determine the Slope
First, calculate the slope using the formula \( m = \frac{{y_2 - y_1}}{{x_2 - x_1}} \). Substituting the given points \( (-7, 1) \) and \( (3, -5) \): \ m = \frac{{-5 - 1}}{{3 - (-7)}} = \frac{{-6}}{{10}} = -\frac{3}{5} \.
02
- Use Point-Slope Form
Using the point-slope form \( y - y_1 = m(x - x_1) \), substitute \( (-7, 1) \) and the calculated slope \( m = -\frac{3}{5} \): \ y - 1 = -\frac{3}{5}(x + 7) \.
03
- Simplify to Slope-Intercept Form
Simplify the equation to put it in the slope-intercept form \( y = mx + b \): \ y - 1 = -\frac{3}{5}(x + 7) \ \ y - 1 = -\frac{3}{5}x - \frac{21}{5} \ \ y = -\frac{3}{5}x - \frac{21}{5} + 1 \ \ y = -\frac{3}{5}x - \frac{21}{5} + \frac{5}{5} \ \ y = -\frac{3}{5}x - \frac{16}{5} \.
04
- Convert to General Form
Rewrite the equation in general form \( Ax + By + C = 0 \): \ y = -\frac{3}{5}x - \frac{16}{5} \ \ 5y = -3x - 16 \ \ 3x + 5y + 16 = 0 \.
05
- Graph the Line
Plot the points \( (-7, 1) \) and \( (3, -5) \) on graph paper. Draw the line passing through these points to visualize the equation \( 3x + 5y + 16 = 0 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
slope calculation
Calculating the slope is the first step in finding the equation of a line. The slope tells us how steep the line is. For any two points \( (x_1, y_1) \) and \( (x_2, y_2) \), the slope \( m \) is given by the formula \( m = \frac{{y_2 - y_1}}{{x_2 - x_1}} \). This relationship measures the vertical change (rise) divided by the horizontal change (run) between the two points.
Let's apply this to our points \( (-7, 1) \) and \( (3, -5) \):
\ m = \frac{{-5 - 1}}{{3 - (-7)}} = \frac{{-6}}{{10}} = -\frac{3}{5} \
This negative slope indicates that the line falls as it moves from left to right.
Let's apply this to our points \( (-7, 1) \) and \( (3, -5) \):
\ m = \frac{{-5 - 1}}{{3 - (-7)}} = \frac{{-6}}{{10}} = -\frac{3}{5} \
This negative slope indicates that the line falls as it moves from left to right.
point-slope form
Point-slope form makes use of the slope and one point on the line. The formula is \( y - y_1 = m(x - x_1) \). This is useful when we already know the slope and at least one point through which the line passes.
Using the calculated slope \( m = -\frac{3}{5} \) and point \( (-7, 1) \):
\ y - 1 = -\frac{3}{5}(x + 7) \
We use this form to quickly plug in the known values without needing to rearrange the equation. This form is especially useful when working out the next step: converting to slope-intercept form.
Using the calculated slope \( m = -\frac{3}{5} \) and point \( (-7, 1) \):
\ y - 1 = -\frac{3}{5}(x + 7) \
We use this form to quickly plug in the known values without needing to rearrange the equation. This form is especially useful when working out the next step: converting to slope-intercept form.
slope-intercept form
The slope-intercept form is \( y = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept (where the line crosses the y-axis). This form is very common in algebra because it clearly shows the slope and the y-intercept.
Starting from point-slope form \( y - 1 = -\frac{3}{5}(x + 7) \), let's simplify:
\begin{align*} y - 1 &= -\frac{3}{5}x - \frac{21}{5} \ y &= -\frac{3}{5}x - \frac{21}{5} + 1 \ y &= -\frac{3}{5}x - \frac{21}{5} + \frac{5}{5} \ y &= -\frac{3}{5}x - \frac{16}{5} \end{align*}
This gives us the slope-intercept form: \( y = -\frac{3}{5}x - \frac{16}{5} \).
Starting from point-slope form \( y - 1 = -\frac{3}{5}(x + 7) \), let's simplify:
\begin{align*} y - 1 &= -\frac{3}{5}x - \frac{21}{5} \ y &= -\frac{3}{5}x - \frac{21}{5} + 1 \ y &= -\frac{3}{5}x - \frac{21}{5} + \frac{5}{5} \ y &= -\frac{3}{5}x - \frac{16}{5} \end{align*}
This gives us the slope-intercept form: \( y = -\frac{3}{5}x - \frac{16}{5} \).
general form
The general form of a linear equation is \( Ax + By + C = 0 \), where \( A \), \( B \), and \( C \) are integers, and \( A \) should be a non-negative integer. This form is particularly useful for solving systems of linear equations and graphing.
From slope-intercept form \( y = -\frac{3}{5}x - \frac{16}{5} \), we need to eliminate fractions and rearrange terms:
\ 5y = -3x - 16 \
\ 3x + 5y + 16 = 0 \
Now we have the general form: \( 3x + 5y + 16 = 0 \). Notice how every coefficient is an integer. This equation can easily be used for various applications, including graphing and analyzing linear systems.
From slope-intercept form \( y = -\frac{3}{5}x - \frac{16}{5} \), we need to eliminate fractions and rearrange terms:
\ 5y = -3x - 16 \
\ 3x + 5y + 16 = 0 \
Now we have the general form: \( 3x + 5y + 16 = 0 \). Notice how every coefficient is an integer. This equation can easily be used for various applications, including graphing and analyzing linear systems.