\(TH1:\left\{{}\begin{matrix}x>0\\y>0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}-\dfrac{1}{3}x^4y^3< 0\\-\dfrac{3}{5}x^3y^4< 0\\\dfrac{1}{2}xy^3>0\end{matrix}\right.\)
\(TH2:\left\{{}\begin{matrix}x< 0\\y< 0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}-\dfrac{1}{3}x^4y^3>0\\-\dfrac{3}{5}x^3y^4>0\\\dfrac{1}{2}xy^3>0\end{matrix}\right.\)
\(TH3:\left\{{}\begin{matrix}x>0\\y< 0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}-\dfrac{1}{3}x^4y^3>0\\-\dfrac{3}{5}x^3y^4< 0\\\dfrac{1}{2}xy^3< 0\end{matrix}\right.\)
\(TH4:\left\{{}\begin{matrix}x< 0\\y>0\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}-\dfrac{1}{3}x^4y^3< 0\\-\dfrac{3}{5}x^3y^4>0\\\dfrac{1}{2}xy^3< 0\end{matrix}\right.\)
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