Chapter 2: Problem 6
Determine whether \(f\) is even, odd, or neither even nor odd. $$f(x)=7 x^{5}-4 x^{3}$$
Short Answer
Expert verified
The function \(f(x) = 7x^5 - 4x^3\) is odd.
Step by step solution
01
Define Even Function
A function is considered even if for every \(x\) in the domain of \(f\), \(f(-x) = f(x)\). This means the graph of the function is symmetrical with respect to the y-axis.
02
Define Odd Function
A function is considered odd if for every \(x\) in the domain of \(f\), \(f(-x) = -f(x)\). This means the graph of the function is symmetrical with respect to the origin.
03
Compute \(f(-x)\)
Substitute \(-x\) into the function \(f(x)\): \[ f(-x) = 7(-x)^5 - 4(-x)^3 = 7(-x^5) - 4(-x^3) = -7x^5 + 4x^3 \]
04
Compare \(f(x)\) and \(f(-x)\) for Even Symmetry
Since \(f(-x) = -7x^5 + 4x^3\) and \(f(x) = 7x^5 - 4x^3\), we have \(f(-x) eq f(x)\). Therefore, \(f(x)\) is not an even function.
05
Check for Odd Symmetry
To confirm if \(f(x)\) is odd, check if \(f(-x) = -f(x)\). Calculate \(-f(x)\): \[ -f(x) = -(7x^5 - 4x^3) = -7x^5 + 4x^3 \]Since this is equal to \(f(-x)\), \(f(x)\) satisfies the condition to be an odd function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Symmetry in Functions
When exploring function symmetries, there are two main types:
- Even Functions: These functions show symmetry about the y-axis. If you fold the graph along the y-axis, both sides would align perfectly.
- Odd Functions: These have symmetry about the origin. This means if you rotate the graph 180 degrees, it would look the same.
Testing Function Parity
Testing whether a function is even, odd, or neither involves a set of straightforward steps:
- Even Parity Test: For a function to be even, substituting \(x\) with \(-x\) must not change the function's expression: \(f(-x) = f(x)\). This suggests a symmetry along the y-axis.
- Odd Parity Test: For a function to be odd, substituting \(x\) with \(-x\) should transform the function into its negative: \(f(-x) = -f(x)\). This indicates symmetry through the origin.
Polynomial Functions
Polynomial functions consist of terms of the form \(a_n x^n\), where \(a_n\) is a constant and \(n\) is a non-negative integer. In the context of testing for evenness or oddness:
- Even-degree terms contribute to even functions. This means terms like \(x^2, x^4\) show no change under \(-x\).
- Odd-degree terms contribute to odd functions. Terms like \(x^3, x^5\) switch signs when \(-x\) is substituted.