Domain of a Composed Function
Algebra · 25th PMO Qualifying Stage
Suppose that a real-valued function $f(x)$ has domain $(-1,1)$. What is the domain of the function $\displaystyle f\left(\frac{3-x}{3+x}\right)$?
A$(0,+\infty)$
B$(-3,3)$
C$(-\infty,-3)$
D$(-\infty,-3)\cup(3,+\infty)$