Which statement best describes how to determine whether f of x is equal to x cubed plus 5 x plus 1 is an even function?

A function is even if replacing x with −x leaves its value unchanged, so test whether f(−x) = f(x). Here f(−x) = (−x)³ + 5(−x) + 1, and f(x) = x³ + 5x + 1. Thus choice B gives the correct comparison for determining whether the function is even.

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