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- $\left( { - 1;1} \right)$.
- $\left( { - \infty ; - 1} \right)$và $\left( {1; + \infty } \right)$.
- $\left( { - 1; + \infty } \right)$.
- $\left( { - \infty ; - 1} \right) \cup \left( {1; + \infty } \right)$.