Let R be the set of real numbers. $f:R→R$ is given by $f(x)=(3-x^3)^{1/3}$, then $f^2$=composition of f with itself=

1/x^3 x^3 x (3-x^3)

x

$f(f(x))=f((3-x^3)^{1/3})=((3-(3-x^3)^{1/3})^3)^{1/3}=(x^3)^{1/3}=x$