Đặt \(\left\{{}\begin{matrix}\sqrt[3]{x^2}=a\ge0\\\sqrt[3]{y^2}=b\ge0\end{matrix}\right.\)
\(P=\sqrt{a^3+a^2b}+\sqrt[]{b^3+ab^2}=\sqrt[]{a^2\left(a+b\right)}+\sqrt[]{b^2\left(a+b\right)}\)
\(=\left(a+b\right)\sqrt[]{a+b}=\sqrt[]{\left(a+b\right)^3}\)
\(Q=2\sqrt[]{\left(a+b\right)^3}\)
Hiển nhiên \(Q>P>0\)