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Ch. 1 - Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 1, Problem 1.6

In Exercises 5–8, determine whether the graph of the function is symmetric about the 𝔂-axis, the origin, or neither.


𝔂 = x²/⁵

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1
To determine symmetry about the y-axis, check if replacing x with -x in the function yields the same function. For the given function y = x^(2/5), replace x with -x to get y = (-x)^(2/5).
Simplify the expression (-x)^(2/5). Since the exponent 2/5 is a positive rational number, (-x)^(2/5) simplifies to x^(2/5) because the square of a negative number is positive.
Since y = (-x)^(2/5) simplifies to y = x^(2/5), the function is symmetric about the y-axis.
To check for symmetry about the origin, replace both x with -x and y with -y in the original equation. This gives -y = (-x)^(2/5).
Since -y = x^(2/5) does not simplify to the original equation y = x^(2/5), the function is not symmetric about the origin. Therefore, the graph of the function is symmetric about the y-axis only.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Symmetry about the y-axis

A function is symmetric about the y-axis if replacing x with -x in the function yields the same output. Mathematically, this means that f(-x) = f(x) for all x in the domain of the function. This type of symmetry indicates that the graph of the function is a mirror image across the y-axis.
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Symmetry about the origin

A function is symmetric about the origin if replacing x with -x and y with -y results in the same function. This is expressed as f(-x) = -f(x). Functions with this symmetry exhibit rotational symmetry of 180 degrees around the origin, meaning that if you rotate the graph, it looks the same.
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Analyzing function symmetry

To determine the symmetry of a function, one can evaluate the function at both x and -x. By comparing the results, one can conclude whether the function is symmetric about the y-axis, the origin, or neither. This analysis is crucial for understanding the behavior of the graph and its visual representation.
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