Chapter 2: Problem 24
19–44 ? Make a table of values and sketch the graph of the equation. Find the x- and y-intercepts and test for symmetry. $$ x+y=3 $$
Short Answer
Expert verified
The x-intercept is (3, 0) and the y-intercept is (0, 3). The graph is a line with negative slope, without symmetry about axes.
Step by step solution
01
Understanding the Equation
The given equation is \(x + y = 3\). This is a linear equation in two variables, \(x\) and \(y\). Our task is to find intercepts, test for symmetry, and plot the graph.
02
Finding the x-intercept
To find the x-intercept, set \(y = 0\) and solve for \(x\).\[\begin{align*} x + 0 &= 3 \ x &= 3 \end{align*}\]Thus, the x-intercept is at \((3, 0)\).
03
Finding the y-intercept
To find the y-intercept, set \(x = 0\) and solve for \(y\).\[\begin{align*} 0 + y &= 3 \ y &= 3 \end{align*}\]Thus, the y-intercept is at \((0, 3)\).
04
Making a Table of Values
Let's create a table of values by choosing different values for \(x\) and calculating corresponding \(y\) values using \(y = 3 - x\).\[\begin{array}{c|c} x & y \\hline 0 & 3 \ 1 & 2 \ 2 & 1 \ 3 & 0 \ 4 & -1 \\end{array}\]
05
Sketching the Graph
Plot the points from the table: \((0, 3), (1, 2), (2, 1), (3, 0), (4, -1)\). Connect the dots with a straight line. This is the graph of \(x + y = 3\), a straight line with a slope of -1.
06
Testing for Symmetry
A linear equation of the form \(Ax + By = C\) is only symmetric about the origin when both \(A\) and \(B\) are non-zero. Since \(x + y = 3\) doesn't change sign upon replacing \(x\) or \(y\) with their negatives, it is only symmetric with respect to itself, having no symmetry about axes or origin.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
X-Intercept
The x-intercept of a graph is the point where the graph crosses the x-axis. At this point, the y-coordinate is zero. To find the x-intercept of the equation \(x + y = 3\), we substitute \(y = 0\) into the equation. Now the equation becomes \(x + 0 = 3\), which simplifies to \(x = 3\). So, the x-intercept is the point \((3, 0)\). This means that the graph will cross the x-axis at the point \( (3, 0) \). Identifying x-intercepts helps in understanding the starting or ending point of a graph along the x-axis.
Y-Intercept
The y-intercept of a graph indicates the point where the graph crosses the y-axis. At this intersecting point, the x-coordinate is zero. For the equation \(x + y = 3\), the y-intercept can be found by substituting \(x = 0\) into the equation. This results in \(0 + y = 3\), which simplifies to \(y = 3\). Thus, the y-intercept is the point \((0, 3)\). This point signifies where the line meets the y-axis, and it is crucial for accurately sketching the graph, as it provides a point from which the line can extend.
Graphing Linear Equations
Graphing linear equations like \(x+y=3\) involves plotting points that satisfy the equation, then drawing a straight line through those points.
- First, select a set of x-values. For each value, compute the corresponding y-value using the equation.
- For instance, choosing x-values such as 0, 1, 2, 3, 4 gives us the points: \((0,3), (1,2), (2,1), (3,0), (4,-1)\).
- Plot these points on a graph, ensuring they are accurately represented.
- Finally, draw a straight line through them, which in this case will have a negative slope, indicating it tilts downward as you move from left to right.
Symmetry in Graphs
Symmetry in graphs is an aspect that reveals how a graph mirrors itself across axes. For linear equations like \(x + y = 3\), the concept of symmetry helps us understand how the graph behaves when coordinates are altered.
- Type of symmetry depends on whether the equation maintains its form when variables are replaced with their negative values.
- A line symmetric about the y-axis remains unchanged if every x is replaced by -x.
- However, being a linear equation, \(x + y = 3\) shows no symmetry about the x or y axes for it doesn't satisfy the criteria for axis or origin symmetry.