Chapter 4: Problem 40
For the following exercises, determine whether the lines given by the equations below are parallel, perpendicular, or neither. $$ \begin{array}{l} 6 x-9 y=10 \\ 3 x+2 y=1 \end{array} $$
Short Answer
Expert verified
The lines are perpendicular.
Step by step solution
01
Convert equations to slope-intercept form
To determine the relationship between the two lines, we first need to convert each equation to the slope-intercept form, which is given by \( y = mx + b \), where \( m \) is the slope.For the first equation, \(6x - 9y = 10\):\[ 9y = 6x - 10 \]\[ y = \frac{6}{9}x - \frac{10}{9} \]Simplifying, we find:\[ y = \frac{2}{3}x - \frac{10}{9} \]So, the slope of the first line is \( \frac{2}{3} \).For the second equation, \(3x + 2y = 1\):\[ 2y = -3x + 1 \]\[ y = -\frac{3}{2}x + \frac{1}{2} \]So, the slope of the second line is \( -\frac{3}{2} \).
02
Compare the slopes
Now that we have both lines in the slope-intercept form, we compare their slopes to determine their relationship.The slope of the first line is \( \frac{2}{3} \), and the slope of the second line is \( -\frac{3}{2} \).
03
Check for parallel lines
Two lines are parallel if their slopes are equal. We compare the slopes \( \frac{2}{3} \) and \( -\frac{3}{2} \). Since these two slopes are not equal, the lines are not parallel.
04
Check for perpendicular lines
Two lines are perpendicular if the product of their slopes is \(-1\). We multiply the slopes of the two lines:\( \frac{2}{3} \times -\frac{3}{2} = -1 \).Since the product of the slopes is \(-1\), the lines are perpendicular.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
The slope-intercept form is a way of writing the equation of a line so that it's easy to see both the slope of the line and where it intercepts the y-axis. This form is expressed as \( y = mx + b \), where:
- \( m \) is the slope of the line.
- \( b \) is the y-intercept, which is the point where the line crosses the y-axis.
- First, isolate \( y \) on one side. Start by subtracting \( 6x \) from both sides to get \( -9y = -6x + 10 \).
- Then, divide every term by \(-9\) to solve for \( y \). You'll end up with \( y = \frac{2}{3}x - \frac{10}{9} \).
Parallel Lines
Parallel lines are lines in a plane that never meet; they are always the same distance apart. For two lines to be parallel, their slopes must be identical.
- This means that for equations in slope-intercept form \( y = m_1x + b_1 \) and \( y = m_2x + b_2 \), the lines are parallel if \( m_1 = m_2 \).
- Consider \( y = \frac{2}{3}x - \frac{10}{9} \) and \( y = -\frac{3}{2}x + \frac{1}{2} \).
- The slopes, \( \frac{2}{3} \) and \(-\frac{3}{2} \), are not equal.
Perpendicular Lines
Perpendicular lines intersect at a right angle, which is 90 degrees. For two lines to be perpendicular, the product of their slopes must be -1.
- For lines with slopes \( m_1 \) and \( m_2 \), they are perpendicular if \( m_1 \times m_2 = -1 \).
- The slope of the first line is \( \frac{2}{3} \), and the second line has a slope of \( -\frac{3}{2} \).
- When multiplying these slopes, \( \frac{2}{3} \times -\frac{3}{2} = -1 \).
Slope
The slope of a line characterizes its steepness and direction. It is a measure of the rate at which the line rises or falls. The slope \( m \) in the equation \( y = mx + b \) can be calculated using the formula:
- \( m = \frac{\text{rise}}{\text{run}} \)
- If a line moves upward from left to right, the slope is positive.
- If it moves downward from left to right, the slope is negative.
- The steeper the line, the larger the absolute value of the slope.