The series $$\sum\limits_{n = 0}^\infty {{1 \over {n!}}\,} $$ converges to

The maximum value of the function $$\,f\left( x \right) = \ln \left( {1 + x} \right) - x$$ (where $$x > - 1$$ ) occurs at $$x=$$________.

If $$z=xy$$ $$ln(xy),$$ then

For $$0 \le t < \infty ,$$ the maximum value of the function $$f\left( t \right) = {e^{ - t}} - 2{e^{ - 2t}}\,$$ occurs at