Try this explanation:
1. if to re-write the given function as:
[tex]y= \frac{e^x}{e^x+C}; \ \ \textless \ =\ \textgreater \ \ y=1- \frac{C}{e^x+C};[/tex]
then it is possible to define its range:
2)
[tex] \lim_{x \to+ \infty}[1- \frac{C}{e^x+C}]=1; \\ \lim_{x \to- \infty}[1- \frac{C}{e^x+C}]=0[/tex]
answer: (0;1)
