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Chapter 1: Problem 77
Find \(k\) so that the line containing the points \((-3, k)\) and \((4,8)\) isparallel to the line containing the points \((5,3)\) and \((1,-6)\)
Short Answer
Expert verified
k = \( \frac{{95}}{{4}} \).
Step by step solution
01
- Find the slope of the line containing points (5, 3) and (1, -6)
To find the slope \(m\frac{{2}}\frac{{1}}\) of a line between two points \( (x_1, y_1) \) and \( (x_2, y_2) \, use the formula \(\frac{{y_2 - y_1}}{{x_2 - x_1}}\). Here, the points are (5, 3) and (1, -6), so \(m = \frac{{-6 - 3}}{{1 - 5}} = \frac{{-9}}{{-4}} = -\frac{{9}}{{4}}s -1\right)}}{\text{4}\right)}}\frac{{6}\frac{{8}\frac{{8}}\frac{{10\ - 14}}}}}}}}\right)}}\rightarrow-\4}}}}\rightarrow.\frac{{3}\frac{{y_2}}} }right}}}}}}}}}}}}}}}}}}}}}}}})}}right}}}}0\)}}}\)}}left-dose}}}}}}}}}}}}}}}}}}}!righ}}}}}}}}}}}}\frac{{68}}-\9\ources}}}}}}}}}}}\displaystyle`}\rightarrow2}}}}}}}
02
- Write down the slope of the line containing points (-3, k) and (4, 8)
Let the slope of this line be m as well. Using the slope formula \(m=\frac{{8 - k}}{{4 - (-3)}}\), we write \(m=\frac{{8 - k}}{{7}}\).
03
- Set the slopes equal (since the lines are parallel)
Since the lines are parallel, their slopes are equal. Therefore, \( \frac{{8 - k}}{{7}} = -\frac{{9}}{{4}} \).
04
- Solve for k
Cross-multiply to solve for k:\(4(8 - k) = -9(7) \rightarrow 32 - 4k = -63 \rightarrow -4k = -63 - 32 \rightarrow -4k = -95 \rightarrow k = \frac{{95}}{{4}}\)
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope Formula
Finding the slope of a line is a crucial step in understanding linear equations and graphs. The slope indicates the steepness and direction of a line.
The formula for finding the slope between two points \( (x_1, y_1) \) and \( (x_2, y_2) \) is: \[ m = \frac{{y_2 - y_1}}{{x_2 - x_1}} \]
Where:
- \( m \) is the slope
- \( (x_1, y_1) \) are the coordinates of the first point
- \( (x_2, y_2) \) are the coordinates of the second point
For instance, in the example given:
- First point: \( (5, 3) \)
- Second point: \( (1, -6) \)
The slope \( m \) can be calculated as:
\[ m = \frac{{-6 - 3}}{{1 - 5}} = \frac{{-9}}{{-4}} = \frac{{9}}{{4}} \]
This slope calculation helps us understand how much the line rises or falls for each unit it moves horizontally.
Parallel Lines
Lines that are parallel have a very special property: they never intersect. This is because they have the same slope.
In our example, we need to ensure that the slope of the line passing through \( (-3, k) \) and \( (4, 8) \) is equal to the slope of the line passing through \( (5, 3) \) and \( (1, -6) \).
Let's find this second slope. Using the slope formula:
\[ m = \frac{{8 - k}}{{4 - (-3)}} = \frac{{8 - k}}{{7}} \]
Now we set this slope equal to the slope of the other line, because the lines are parallel and must have the same slope.
\[ \frac{{8 - k}}{{7}} = \frac{{9}}{{4}} \]
This equation helps us find the unknown \( k \) value. By solving this equation, we can determine the y-coordinate of the point \( (-3, k) \) that will make the lines parallel.
Solving Equations
To find the value of \( k \) that makes the slopes equal (and thus the lines parallel), we need to solve the equation:
\[ \frac{{8 - k}}{{7}} = \frac{{9}}{{4}} \]
We can use cross-multiplication to solve this equation. Cross-multiplication involves multiplying the numerator of one fraction by the denominator of the other fraction and vice versa. This clears the fractions and simplifies the equation:
\[ 4(8 - k) = 9(7) \]
\[ 32 - 4k = 63 \]
\[ -4k = 63 - 32 \]
\[ -4k = 95 \]
Finally, divide both sides by -4 to solve for \( k \):
\[ k = \frac{{95}}{{4}} \]
This solution shows that \( k = \frac{{95}}{{4}} \) satisfies the parallel condition for the given lines. Understanding how to solve equations like this is essential for tackling a wide range of mathematical problems.
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