Điều kiện: \(\hept{\begin{cases}3\left(x+y\right)\ne0\\x^2-2xy+y^2\ne0\\6\left(x+y\right)\ne0\end{cases}\Rightarrow}\hept{\begin{cases}x+y\ne0\\\left(x-y\right)^2\ne0\\x+y\ne0\end{cases}\Rightarrow\hept{\begin{cases}x\ne-y\\x\ne y\end{cases}}}\)
\(\frac{2x^3-2y^3}{3x+3y}:\frac{x^2-2xy+y^2}{6x+6y}\)
\(=\frac{2\left(x^3-y^3\right)}{3\left(x+y\right)}.\frac{6\left(x+y\right)}{\left(x-y\right)^2}\)
\(=\frac{2\left(x-y\right)\left(x^2+xy+y^2\right)}{3\left(x+y\right)}.\frac{6\left(x+y\right)}{\left(x-y\right)^2}\)
\(=\frac{4\left(x^2+xy+y^2\right)}{x-y}\)