Chapter 1: Problem 69
Make a table of values, and sketch the graph of the equation. Find the x- and y-intercepts, and test for symmetry. (a) \(y=\sqrt{4-x^{2}}\) (b) \(x=y^{3}+2 y\)
Short Answer
Expert verified
Equation (a) is a semi-circle with x-intercepts at -2, 2 and y-intercept at 2; it's symmetric about the y-axis. Equation (b) has y-intercept 0 without symmetry or x-intercepts.
Step by step solution
01
Understanding Equation (a)
The equation is given as \(y = \sqrt{4 - x^2}\). This is a semi-circle function as the square root restricts the graph to be non-negative, implying it represents the upper half of a circle centered at the origin \((0,0)\) with a radius of 2. First, we'll identify the domain of \(x\), which must satisfy \(4 - x^2 \geq 0\), leading to the domain \([-2, 2]\).
02
Making a Table of Values for Equation (a)
Let's choose values of \(x\) within the domain \([-2, 2]\) and compute corresponding \(y\) values:- For \(x = -2\), \(y = \sqrt{4 - (-2)^2} = 0\).- For \(x = -1\), \(y = \sqrt{4 - (-1)^2} = \sqrt{3}\).- For \(x = 0\), \(y = \sqrt{4 - 0^2} = 2\).- For \(x = 1\), \(y = \sqrt{4 - 1^2} = \sqrt{3}\).- For \(x = 2\), \(y = \sqrt{4 - 2^2} = 0\).
03
Finding Intercepts for Equation (a)
The y-intercept is at \(x = 0\), giving \(y = 2\). The x-intercepts occur when \(y = 0\), so solving \(\sqrt{4 - x^2} = 0\), gives \(x = \pm 2\). Thus, the x-intercepts are \((2, 0)\) and \((-2, 0)\).
04
Checking Symmetry for Equation (a)
The equation \(y = \sqrt{4-x^2}\) is symmetrical about the y-axis because substituting \(-x\) for \(x\) results in the same equation. Hence, it exhibits even symmetry.
05
Understanding Equation (b)
The equation is given as \(x = y^3 + 2y\). This curve is defined implicitly. First, determine what x and y values are feasible.
06
Making a Table of Values for Equation (b)
Choose various values for \(y\) to find corresponding \(x\) values:- For \(y = -2\), \(x = (-2)^3 + 2(-2) = -12\).- For \(y = -1\), \(x = (-1)^3 + 2(-1) = -3\).- For \(y = 0\), \(x = 0^3 + 2(0) = 0\).- For \(y = 1\), \(x = 1^3 + 2(1) = 3\).- For \(y = 2\), \(x = 2^3 + 2(2) = 12\).
07
Finding Intercepts for Equation (b)
The y-intercept is where \(x = 0\), giving \(y = 0\). There are no x-intercepts because there is no \(y\) that satisfies \(x = 0\) when \(x\) itself is set to 0 other than \(y = 0\).
08
Checking Symmetry for Equation (b)
Substitute \(-y\) for \(y\) in \(x = y^3 + 2y\) resulting in \(x = -y^3 - 2y\). This is neither symmetric across the y-axis nor the x-axis. By changing \(x\) to \(-x\) or \(y\) to \(-y\), the original equation form is not preserved, indicating there is no symmetry.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
x- and y-intercepts
The x- and y-intercepts are points where a graph crosses the x-axis and y-axis, respectively. These intercepts give us valuable information about a graph's shape and position.
For the equation \(y = \sqrt{4 - x^2}\), let's identify the intercepts:
For the equation \(y = \sqrt{4 - x^2}\), let's identify the intercepts:
- The **y-intercept** occurs where \(x = 0\). By substituting \(x = 0\) in the equation, we find \(y = \sqrt{4 - 0^2} = 2\). This means the graph crosses the y-axis at the point \((0, 2)\).
- The **x-intercepts** occur where \(y = 0\). Solving \(\sqrt{4 - x^2} = 0\) gives us \(x^2 = 4\), so \(x = \pm 2\). This indicates the graph crosses the x-axis at the points \((2, 0)\) and \((-2, 0)\).
- The **y-intercept** is found by setting \(x = 0\), giving us \(y = 0\). Thus, the graph crosses the y-axis at \((0, 0)\).
- There are no additional **x-intercepts** for \(x = y^3 + 2y\) at values of \(x = 0\), as the only solution is \(y = 0\). Hence, it does not cross the x-axis elsewhere.
symmetry in graphs
Symmetry in graphs tells us whether a graph is mirrored across a certain line. This can help simplify graphing by reducing the need to plot every point.
With the function \(y = \sqrt{4-x^2}\), we have even symmetry because the equation remains unchanged when substituting \(-x\) for \(x\). This means:
With the function \(y = \sqrt{4-x^2}\), we have even symmetry because the equation remains unchanged when substituting \(-x\) for \(x\). This means:
- The graph is symmetric about the **y-axis**, as the positive and negative x-values yield identical y-values.
- Substituting \(-y\) for \(y\) does not lead the equation back to itself, and similarly with \(x\).
- This indicates there is **no symmetry** about either axis or the origin for this graph.
table of values
Creating a table of values is a fundamental step in graphing an equation. It involves selecting values for one variable and calculating the corresponding values for the other variable. This step lays the groundwork for accurately plotting a graph.
For equation \(y = \sqrt{4 - x^2}\):
For equation \(y = \sqrt{4 - x^2}\):
- Choose values of \(x\) from its domain \([-2, 2]\).
- Calculate the corresponding \(y\) values using the equation:
- For \(x = -2\), \(y = 0\).
- For \(x = -1\), \(y = \sqrt{3}\).
- For \(x = 0\), \(y = 2\).
- For \(x = 1\), \(y = \sqrt{3}\).
- For \(x = 2\), \(y = 0\).
- Choose various values for \(y\).
- Compute the corresponding \(x\) values:
- For \(y = -2\), \(x = -12\).
- For \(y = -1\), \(x = -3\).
- For \(y = 0\), \(x = 0\).
- For \(y = 1\), \(x = 3\).
- For \(y = 2\), \(x = 12\).
semi-circle function
The semi-circle function is a specific kind of function involving a square root which produces a circular graph but only in half, typically allowing only non-negative values.
The function \(y = \sqrt{4 - x^2}\) is an example of a semi-circle function as it represents the upper half of a circle. Here’s how you can identify such a function:
The function \(y = \sqrt{4 - x^2}\) is an example of a semi-circle function as it represents the upper half of a circle. Here’s how you can identify such a function:
- This semi-circle is centered at the point \((0,0)\), with a radius of 2.
- The domain is restricted because the square root is defined only for non-negative values, hence, the values of \(x\) must satisfy \(4 - x^2 \geq 0\).
- This creates a graph that extends from \(x = -2\) to \(x = 2\).
- Notice that the radius determines the range of the function, here from 0 to 2.