Please reason step by step, and put your final answer within \boxed{}.
Among the four expressions $\sqrt[4]{(-4)^{2n}}$, $\sqrt[4]{(-4)^{2n+1}}$, $\sqrt[5]{{x}^{2}}$, and ${\sqrt[5]{-x^{2}}(n∈N)}$, the ones that are meaningful are ______.
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