Chapter 2: Problem 8
Describe the set of all points \(P(x, y)\) in a coordinate plane that satisfy the given condition. (a) \(y=-2\) (b) \(x=4\) (c) \(x / y<0\) (d) \(x y=0\) (e) \(y>1\) (f) \(y=0\)
Short Answer
Expert verified
(a) Horizontal line at y = -2, (b) vertical line at x = 4, (c) x and y have opposite signs, (d) x or y is 0, (e) region above y = 1, (f) x-axis.
Step by step solution
01
Identify type of graph for equation y = -2
The equation \(y = -2\) represents a horizontal line in the coordinate plane. This line passes through all points where the y-coordinate is -2, regardless of the x-coordinate.
02
Identify type of graph for equation x = 4
The equation \(x = 4\) represents a vertical line in the coordinate plane. This line passes through all points where the x-coordinate is 4, regardless of the y-coordinate.
03
Analyze condition x/y < 0
The condition \(x / y < 0\) implies that the signs of x and y must be opposite for the inequality to hold. Thus, this condition describes the set of points where either x is positive and y is negative or x is negative and y is positive.
04
Analyze condition xy = 0
The condition \(xy = 0\) means that either x or y (or both) must be zero. This describes the set of points on the x-axis (y=0) and the y-axis (x=0), including the origin (0,0).
05
Identify region for inequality y > 1
The inequality \(y > 1\) describes the region above the horizontal line \(y = 1\) in the coordinate plane. This includes all points where the y-coordinate is greater than 1.
06
Identify type of graph for equation y = 0
The equation \(y = 0\) represents the x-axis itself, which includes all points where the y-coordinate is zero.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Horizontal Line
A horizontal line in the coordinate plane is represented by an equation in the form of \(y = c\), where \(c\) is a constant. This means that no matter what value \(x\) takes, the \(y\)-value remains constant.
For example, in the exercise, the equation \(y = -2\) signifies that the line passes through the y-coordinate -2 across all values of \(x\). This creates a line that moves from left to right horizontally.
**Characteristics of Horizontal Lines:**
For example, in the exercise, the equation \(y = -2\) signifies that the line passes through the y-coordinate -2 across all values of \(x\). This creates a line that moves from left to right horizontally.
**Characteristics of Horizontal Lines:**
- Parallel to the x-axis.
- Do not cross or touch the y-axis, except at the specified y-value.
- Every point on the line has the same y-value.
Vertical Line
Vertical lines in the coordinate plane are defined by equations of the form \(x = c\), where \(c\) is a constant value for the x-coordinate, no matter what the y-coordinate is.
As in our exercise with \(x = 4\), this creates a line that intersects the x-axis at the point (4,0) and extends infinitely up and down. All the points on this line share the same x-coordinate.
**Characteristics of Vertical Lines:**
As in our exercise with \(x = 4\), this creates a line that intersects the x-axis at the point (4,0) and extends infinitely up and down. All the points on this line share the same x-coordinate.
**Characteristics of Vertical Lines:**
- Parallel to the y-axis.
- Every point on the line has the same x-value.
- They do not have a slope (the slope is undefined).
Inequality
Inequalities describe a range or set of points that do not strictly lie on one particular line but satisfy a condition, like \(x/y < 0\). This means both signs must be opposite for the inequality to hold.
In simpler terms, the inequality states that:
Inequalities are foundational in linear programming, optimization tasks, and many real-world applications requiring range-based conditions.
In simpler terms, the inequality states that:
- If \(x\) is positive, \(y\) should be negative.
- If \(x\) is negative, \(y\) should be positive.
Inequalities are foundational in linear programming, optimization tasks, and many real-world applications requiring range-based conditions.
Axes
Coordinate planes feature two primary reference lines: the x-axis and the y-axis.
**The x-axis** is the horizontal plane where \(y = 0\). Points on this axis have no vertical component. For example, \(y = 0\) in an equation defines the x-axis itself.
**The y-axis** is the vertical plane where \(x = 0\). Here, points have no horizontal component. Together, these axes intersect at the origin point, (0,0).
**Significance of Axes:**
**The x-axis** is the horizontal plane where \(y = 0\). Points on this axis have no vertical component. For example, \(y = 0\) in an equation defines the x-axis itself.
**The y-axis** is the vertical plane where \(x = 0\). Here, points have no horizontal component. Together, these axes intersect at the origin point, (0,0).
**Significance of Axes:**
- They act as reference lines for other graphed lines or points.
- Crossing points on these axes often determine specific lines or conditions, like \(xy = 0\) indicating points on either axis.
- Used to divide the plane into quadrants aiding in graph analysis.