Consider the function $$f(x) = {{27({x^{2/3}} - x)} \over 4}$$.

How many solutions does the function f(x) = $$-$$ 1 have?

The inverse of the function y = 5^{ln x} is

The function f(x) = | x | $$-$$ x³ is

If x is any real number, then $${{{x^2}} \over {1 + {x^4}}}$$ belongs to which one of the following intervals?