If $$f({x_1}) - f({x_2}) = f\left( {{{{x_1} - {x_2}} \over {1 - {x_1}{x_2}}}} \right)$$ for x₁, x₂ $$\in$$($$-$$1, 1), then what is f(x) equal to ?

What is the range of the function $$y = {{{x^2}} \over {1 + {x^2}}}$$ where x$$\in$$R ?

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

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

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

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