Chapter 2: Problem 22
\(19-32\) Sketch the region given by the set. $$ \\{(x, y) | y=-2\\} $$
Short Answer
Expert verified
The region is a horizontal line at \( y = -2 \) extending infinitely along the x-axis.
Step by step solution
01
Identify the Equation
The given set is \( \{(x, y) | y = -2 \} \). This represents all the points \((x, y)\) where the y-coordinate is -2.
02
Understand the Graph of the Equation
The equation \( y = -2 \) is a horizontal line. For any value of \( x \), the \( y \) coordinate remains constant at -2. Therefore, this line is parallel to the x-axis.
03
Determine the Range of x-values
Since no restrictions are given for \( x \), \( x \) can be any real number. This implies that the line extends infinitely in both positive and negative x-directions.
04
Sketch the Region
To sketch the line \( y = -2 \), draw a horizontal line that crosses the y-axis at -2. This line will extend left and right indefinitely, parallel to the x-axis.
05
Verify the Sketch
Ensure the line is correctly positioned by checking that all points on the line have a y-coordinate of -2, confirming it represents the set \( \{ (x, y) | y = -2 \} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Horizontal Lines
A horizontal line in coordinate geometry has a constant y-value across all points. This means for a horizontal line like our example, where the equation is \( y = -2 \), the y-coordinate of every point on the line doesn't change; it stays at -2 no matter what the x-coordinate is. This creates a perfectly straight line parallel to the x-axis.
Horizontal lines are unique because:
Horizontal lines are unique because:
- They do not tilt or slope; they remain flat.
- They extend infinitely in the left and right directions along the x-axis.
The Y-axis in Graphs
The y-axis is one of the two main axes in a two-dimensional graph. It runs vertically and is used to determine the vertical position of a point. In the context of our problem, the y-axis helps to identify where the horizontal line \( y = -2 \) crosses.
It’s important to remember:
It’s important to remember:
- The y-axis represents the set of possible y-values for points in the plane.
- The y-coordinate of any point on the y-axis is zero in a standard coordinate system, except where specified otherwise (as in the set {\( (x, y) | y = -2 \)}).
The Role of Real Numbers
Real numbers in coordinate geometry define the values that coordinates can take. In our problem, when we say \( x \) can be any real number, it means there are no boundaries on how far left or right the x-values can extend.
Real numbers are crucial because:
Real numbers are crucial because:
- They allow lines, such as \( y = -2 \), to extend infinitely.
- They include both positive and negative numbers as well as zero, covering the entire x-axis.
- They ensure continuity, meaning there are no gaps in the line on the graph.
Basic Techniques in Graph Sketching
Graph sketching is a fundamental skill in coordinate geometry. To sketch a line like \( y = -2 \), first identify its nature (in this case, a horizontal line). Begin by locating the y-coordinate on the y-axis. For \( y = -2 \), this means finding \( y = -2 \) on the axis and drawing a straight, horizontal line through it.
Here's how to make sure your sketch is accurate:
Here's how to make sure your sketch is accurate:
- Ensure the line is parallel to the x-axis. Use a ruler if necessary to maintain straightness.
- Verify the line crosses the y-axis at the correct point, \( y = -2 \).
- Check a sample of points on the line to confirm they all have the same y-coordinate (-2 here).