Chapter 1: Problem 62
Determine whether \(f\) is even, odd, or neither. If you have a graphing calculator, use it to check your answer visually. $$f(x)=x|x|$$
Short Answer
Expert verified
The function \( f(x) = x|x| \) is odd.
Step by step solution
01
Function Definition
The function given is \( f(x) = x|x| \). Here, \(|x|\) denotes the absolute value of \(x\). The absolute value function is defined as \(|x| = x\) if \(x \geq 0\) and \(|x| = -x\) if \(x < 0\). We need to evaluate whether this function is even, odd, or neither.
02
Even Function Test
A function \( f(x) \) is even if \( f(-x) = f(x) \) for all \(x\). Let's calculate \( f(-x) \). Substitute \(-x\) in place of \(x\):\[ f(-x) = -x|-x| \]Using the property of absolute values, \(|-x| = |x|\), we get:\[ f(-x) = -x|x| \]For \( f(x) \) to be even, \( f(-x) \) must equal \( x|x| \), but clearly \( -x|x| eq x|x| \) if \( x eq 0\). Therefore, \( f(x) \) is not even.
03
Odd Function Test
A function \( f(x) \) is odd if \( f(-x) = -f(x) \) for all \(x\). We previously found that:\[ f(-x) = -x|x| \]Now, calculate \(-f(x)\):\[ -f(x) = -(x|x|) = -x|x| \]Since \( f(-x) = -f(x) \), \( f(x) = x|x| \) satisfies the condition for odd functions.
04
Conclusion
Since the condition \( f(-x) = -f(x) \) holds for all \(x\), the function \( f(x) = x|x| \) is an odd function.
05
Visual Verification (Optional)
If you have a graphing calculator, you can graph \( f(x) = x|x| \) to visually check its symmetry. An odd function is symmetric about the origin, meaning it will look the same if rotated 180 degrees around the origin.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Even and Odd Functions
Understanding whether a function is even, odd, or neither is a fundamental concept in algebra. It helps to predict the behavior and symmetry of the function's graph. Here’s how you can determine if a function is even or odd:
- A function is even if for every input value, the output is the same when the input is replaced by its negative. Mathematically, this means: \( f(-x) = f(x) \) for all \( x \).
- A function is odd if for every input value, the output is the negative of what it is when the input is replaced by its negative. This condition is expressed as: \( f(-x) = -f(x) \) for all \( x \).
- If neither of these conditions is met, the function is neither even nor odd.
Absolute Value Function
The absolute value function, denoted by \( |x| \), is a basic yet crucial function in mathematics. It represents the "magnitude" or "distance" of a number from zero on the number line and is always non-negative. Here's how the absolute value function works:
- If \( x \geq 0 \), then \( |x| = x \).
- If \( x < 0 \), then \( |x| = -x \).
Graphing Calculator
Graphing calculators are excellent tools for visualizing mathematical functions and concepts, including symmetry and transformations. If you can use a graphing calculator, here's how it can help with this type of problem:
- Input the function \( f(x) = x|x| \) into the calculator.
- Use the graphing feature to sketch the function's graph.
- Observe the graph for aspects of symmetry. An odd function will show symmetry through rotation around the origin, depicted as a consistent curve opposite from each side.
- This visual feedback provides intuitive confirmation of algebraic findings.
Function Verification
Verifying the properties of a function involves several systematic steps. It ensures that abstract mathematical definitions are consistent with computational results. Here’s a brief walkthrough of the function verification process, specifically for even and odd functions:
- Calculate \( f(-x) \) and compare it algebraically to \( f(x) \) and \(-f(x)\).
- Determine if \( f(-x) = f(x) \) (for evenness) or \( f(-x) = -f(x) \) (for oddness).
- For our function \( f(x) = x|x| \), we calculated \( f(-x) = -x|x| \), which matched \(-f(x)\), confirming odd symmetry.
- As a supplementary check, use visual methods, like a graphing calculator, to corroborate findings.