Determine the set of xxx such that x2−1x2+1<0\frac{x^2-1}{x^2+1} < 0x2+1x2−1<0.
x∈(−1,1)x \in (-1, 1)x∈(−1,1)
x∈(−∞,−1)∪(1,∞)x \in (-\infty, -1) \cup (1, \infty)x∈(−∞,−1)∪(1,∞)
x∈Rx \in \mathbb{R}x∈R
x∈∅x \in \emptysetx∈∅