\(\dfrac{3P+3}{P-1}>0\\↔\dfrac{3(P+1)}{P-1}>0\\↔\dfrac{P+1}{P-1}>0\\↔\left[\begin{array}{1}\begin{cases}P+1>0\\P-1>0\end{cases}\\\begin{cases}P+1<0\\P-1<0\end{cases}\end{array}\right.\\↔\left[\begin{array}{1}\begin{cases}P>-1\\P>1\end{cases}\\\begin{cases}P<-1\\P<1\end{cases}\end{array}\right.\\↔\left[\begin{array}{1}P>1\\P<-1\end{array}\right.\)
Vậy \(\dfrac{3P+3}{P-1}>0\) khi \(P>1\) hoặc \(P<-1\)