Đáp án:
\(\begin{array}{l}
f\left( x \right) > 0 \Leftrightarrow x \in \left( { - 1;0} \right) \cup \left( {1; + \infty } \right)\\
f\left( x \right) < 0 \Leftrightarrow x \in \left( { - \infty ; - 1} \right) \cup \left( {0;1} \right)
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
Xét:x - 1 = 0 \to x = 1\\
x + 1 = 0 \to x = - 1\\
x = 0
\end{array}\)
BXD:
x -∞ -1 0 1 +∞
x+1 - 0 + / + / +
x-1 - / - / - 0 +
x - / - 0 + / +
f(x) - // + 0 - // +
\(\begin{array}{l}
KL:f\left( x \right) > 0 \Leftrightarrow x \in \left( { - 1;0} \right) \cup \left( {1; + \infty } \right)\\
f\left( x \right) < 0 \Leftrightarrow x \in \left( { - \infty ; - 1} \right) \cup \left( {0;1} \right)
\end{array}\)
