The correct answer is option D. Which is the even function is f (x) = x⁴.
<h3>What is an even function?</h3>
The function in which when the sign of the input variable is changed the output remains the same is called the even function. Mathematically we can write it as f(x) = f(-x ).
let us check the given four options:-
A f(x) = √x ; f(-x) = √-x here f(x) ≠ f(-x)
B f(x) = x ; f(-x) = -x here f(x) ≠ f(-x)
C f(x) = x³ + 1 ; f(-x) = -x³ + 1 here f(x) ≠ f(-x)
D f(x) = x⁴ ; f(-x) = (-x)⁴ = x⁴ here f(x) = f(-x)
We can see that in the option D the f(x) = x⁴ is an even function because f(x) = f(-x).
Therefore the correct answer is option D. Which is the even function is f (x) = x⁴.
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