Let P , Q ∈ R [ X ] {\displaystyle {}P,Q\in \mathbb {R} [X]} be polynomials and let U := { x ∈ R ∣ Q ( x ) ≠ 0 } {\displaystyle {}U:={\left\{x\in \mathbb {R} \mid Q(x)\neq 0\right\}}} .
rational function
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