\(g(x) \frac{3x}{x^{2}-81} \\ \\ D: x^{2}-81
eq 0 \\ \\ (x-9)(x+9)
eq 0 \\ \\ x-9
eq 0 \ \vee \ x+9
eq 0 \\ \\ x
eq 9 \ \vee \ x
eq -9 \\ \\ x\in R \ \setminus \lbrace -9,9 \rbrace \\ \\ x\in (-\infty,-9) \ \cup \ (-9, 9) \ \cup \ (9,+\infty)\)
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