Question
Let $f: \mathbb{R} \rightarrow \mathbb{R}$ be a function defined by $f(x)=\frac{x}{\left(1+x^4\right)^{1 / 4}}$, and $g(x)=f(f(f(f(x))))$. Then, $18 \int_0^{\sqrt{2 \sqrt{5}}} x^2 g(x) d x$ is equal to
Let $f: \mathbb{R} \rightarrow \mathbb{R}$ be a function defined by $f(x)=\frac{x}{\left(1+x^4\right)^{1 / 4}}$, and $g(x)=f(f(f(f(x))))$. Then, $18 \int_0^{\sqrt{2 \sqrt{5}}} x^2 g(x) d x$ is equal to