Chapter 15: Problem 54
Determine whether each pair of lines is parallel, perpendicular, or neither. \(y=\frac{1}{3} x-7\) \(y+3 x=1\)
Short Answer
Expert verified
The lines are perpendicular.
Step by step solution
01
- Write Both Equations in Slope-Intercept Form
The slope-intercept form of a line is given by the equation: \[ y = mx + b \] where \( m \) is the slope and \( b \) is the y-intercept. The first line is already in this form: \[ y = \frac{1}{3} x - 7 \]The second line equation \( y + 3x = 1 \) needs to be rearranged to find the slope and y-intercept: Subtract \(3x\) from both sides to get:\[ y = -3x + 1 \]
02
- Identify Slopes of Both Lines
From the slope-intercept form: First line: \( y = \frac{1}{3} x - 7 \), the slope \( m_1 = \frac{1}{3} \) Second line: \( y = -3x + 1 \), the slope \( m_2 = -3 \)
03
- Determine Relationship Between Slopes
To determine if lines are parallel, perpendicular, or neither: Two lines are parallel if their slopes are equal: \( m_1 = m_2 \) Two lines are perpendicular if the product of their slopes is \(-1\): \( m_1 \times m_2 = -1 \)Otherwise, the lines are neither. In this case: \( \frac{1}{3} \times -3 = -1 \) which satisfies the condition for perpendicular lines.
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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 of a line's equation is a way to describe a line algebraically. It is written as: \[ y = mx + b \] In this format, \( y \) represents the y-coordinate of any point on the line, \( x \) represents the x-coordinate, \( m \) is the slope of the line, and \( b \) is the y-intercept, which is where the line crosses the y-axis. This form is very useful for graphing lines and understanding their behavior. For example, a line in slope-intercept form makes it easy to see how steep the line is and where it starts on the y-axis. The exercise involved converting both lines to this form, which made it simpler to identify their slopes and compare them.
slope
The slope of a line measures its steepness or incline. Mathematically, it is defined as the ratio of the vertical change to the horizontal change between two points on the line: \[ m = \frac{{\text{{change in y}}}}{{\text{{change in x}}}} \] The slope can tell us a lot about the line:
- A positive slope means the line goes up as you move from left to right.
- A negative slope means the line goes down as you move from left to right.
- A slope of zero means the line is horizontal.
- An undefined slope (division by zero) means the line is vertical.
line equations
Line equations help us describe the relationship between x and y coordinates on a Cartesian plane. Common forms of line equations include:
- Slope-intercept form: \[ y = mx + b \]
- Standard form: \[ Ax + By = C \]
- Point-slope form: \[ y - y_1 = m(x - x_1) \]
algebra
Algebra is the branch of mathematics dealing with symbols and the rules for manipulating those symbols. It helps us represent real-world relationships using equations and formulas. Understanding how to manipulate these equations is crucial for solving various problems. In the given exercise, algebra was used to:
- Convert the equation \( y + 3x = 1 \) into slope-intercept form \( y = -3x + 1 \)
- Identify and compare the slopes of two lines
- Determine their geometric relationship (parallel, perpendicular, or neither)