The set of all points, where the function $$f(x) = \sqrt {1 - {e^{ - {x^2}}}} $$ is differentiable, is

If $$f(x) = x(\sqrt x - \sqrt {x + 1} )$$, then f(x) is

Let g be the greatest integer function. Then, the function f(x) = (g(x))² $$-$$ g(x) is discontinuous at

What is $$\mathop {\lim }\limits_{x \to 0} {{{e^x} - (1 + x)} \over {{x^2}}}$$ equal to ?