Chapter 2: Problem 20
Explain why \(f\) is continuous on the given interval or intervals $$ f(x)=\sqrt{x^{2}-x^{4}} ;[-1,1] $$
Short Answer
Expert verified
The function \(f(x) = \sqrt{x^2 - x^4}\) is continuous on \([-1, 1]\) because it is defined and involves continuous operations under the given conditions.
Step by step solution
01
First Check the Domain of the Function
The function given is \(f(x) = \sqrt{x^2 - x^4}\). For \(f(x)\) to be defined, the expression under the square root, \(x^2 - x^4\), must be non-negative because the square root of a negative number is not real. Hence, we set up the inequality \(x^2 - x^4 \geq 0\).
02
Factor and Analyze the Inequality
Rearrange \(x^2 - x^4 \geq 0\) as \(x^2(1 - x^2) \geq 0\). This requires that both \(x^2 \geq 0\) and \(1 - x^2 \geq 0\). Since \(x^2 \geq 0\) for all real \(x\), we focus on \(1 - x^2 \geq 0\) which simplifies to \(-1 \le x \le 1\). So the function is defined on the interval \([-1, 1]\).
03
Check the Continuity on the Domain
A function is continuous if it is continuous at every point in its domain. \(f(x) = \sqrt{x^2 - x^4}\) is a composition of continuous functions \(x^2, x^4\), and \(\sqrt{\cdot}\), which are continuous on their domains. Hence, \(f(x)\) is continuous on \([-1, 1]\) because these are all simple algebraic operations and square root of non-negative expressions.
04
Verify End Points of the Interval
Check the function at the endpoints \(x = -1\) and \(x = 1\) to ensure continuity over the closed interval. Substituting yields \(f(-1) = \sqrt{1 - (-1)^4} = 0\) and \(f(1) = \sqrt{1 - 1^4} = 0\). \(f(x)\) returns a real number at these endpoints and agrees with the behavior in the interval, showing no discontinuity.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
The domain of a function defines the set of all possible input values (x-values) for which the function is defined and produces a real number output. When dealing with the function \(f(x) = \sqrt{x^2 - x^4}\), the challenge is to determine for which \(x\) values this function yields real outputs since the square root of a negative number isn't defined in the set of real numbers.
Finding the domain involves identifying when the expression under the square root, \(x^2 - x^4\), is greater than or equal to zero. This results in the inequality \(x^2 - x^4 \geq 0\). If this inequality holds, the function is defined.
Considering the factors separately, \(x^2\) is always non-negative for real numbers, as it represents square values. Thus, the critical part of the inequality that needs more focus is \(1 - x^2 \geq 0\). Solving this inequality reveals that the solution falls between \(-1\) and \(1\), inclusive. Therefore, the domain of the function \(f(x)\) is \([-1, 1]\). This is where the function exists continuously.
Finding the domain involves identifying when the expression under the square root, \(x^2 - x^4\), is greater than or equal to zero. This results in the inequality \(x^2 - x^4 \geq 0\). If this inequality holds, the function is defined.
Considering the factors separately, \(x^2\) is always non-negative for real numbers, as it represents square values. Thus, the critical part of the inequality that needs more focus is \(1 - x^2 \geq 0\). Solving this inequality reveals that the solution falls between \(-1\) and \(1\), inclusive. Therefore, the domain of the function \(f(x)\) is \([-1, 1]\). This is where the function exists continuously.
Inequality Analysis
Analyzing inequalities is crucial for defining the domain of functions, especially those involving square roots. The given function \(f(x) = \sqrt{x^2 - x^4}\) involves setting up and solving an inequality to find when the expression under the square root is non-negative.
The inequality \(x^2 - x^4 \geq 0\) is established because a square root cannot process negative numbers in the real number system. By factoring the expression, we rewrite it as \(x^2(1 - x^2) \geq 0\), focusing on when each multiplicative term is greater than or equal to zero.
We know \(x^2\) is always non-negative, thus the condition \(1 - x^2 \geq 0\) dictates our solution. Solving \(1 - x^2 \geq 0\) brings us to understand the bounds: \(-1 \leq x \leq 1\). Through this analysis, we confine the function's domain, ensuring values where it returns real, defined outcomes.
The inequality \(x^2 - x^4 \geq 0\) is established because a square root cannot process negative numbers in the real number system. By factoring the expression, we rewrite it as \(x^2(1 - x^2) \geq 0\), focusing on when each multiplicative term is greater than or equal to zero.
We know \(x^2\) is always non-negative, thus the condition \(1 - x^2 \geq 0\) dictates our solution. Solving \(1 - x^2 \geq 0\) brings us to understand the bounds: \(-1 \leq x \leq 1\). Through this analysis, we confine the function's domain, ensuring values where it returns real, defined outcomes.
Algebraic Operations
Algebraic operations are the backbone of analyzing mathematical functions. For a function like \(f(x) = \sqrt{x^2 - x^4}\), it is formed through a series of basic algebraic manipulations or operations. Here, each operation must precisely follow mathematical principles to ensure correctness.
The function is derived from powers of \(x\), specifically \(x^2\) and \(x^4\), which are common polynomial expressions. Dealing with powers involves the principles of squaring and raising numbers to their respective power of four. The resulting expression \(x^2 - x^4\) is designed to fit within the square root.
Simplifying such functions needs careful algebraic steps. Simplifications can occasionally reshape the expression's domain. Factoring \(x^2(1-x^2)\) involves using distributive properties and recognizing common forms and differences of squares. These are fundamental algebraic tools that aid in understanding when and why a function is continuous and defined over specific intervals.
The function is derived from powers of \(x\), specifically \(x^2\) and \(x^4\), which are common polynomial expressions. Dealing with powers involves the principles of squaring and raising numbers to their respective power of four. The resulting expression \(x^2 - x^4\) is designed to fit within the square root.
Simplifying such functions needs careful algebraic steps. Simplifications can occasionally reshape the expression's domain. Factoring \(x^2(1-x^2)\) involves using distributive properties and recognizing common forms and differences of squares. These are fundamental algebraic tools that aid in understanding when and why a function is continuous and defined over specific intervals.