Đáp án:
$\begin{array}{l}
8)\\
H = {\left( {2x - y} \right)^3} + {\left( {3x + 2} \right)^2}\\
- {\left( {y + 2} \right)^3} - {\left( {x - 3y} \right)^2}\\
= 8{x^3} - 3.4{x^2}.y + 3.2x.{y^2} - {y^3}\\
+ 9{x^2} + 12x + 4\\
- \left( {{y^3} + 6{y^2} + 12y + 8} \right) - {x^2} + 6xy - {y^2}\\
= 8{x^3} + 8{x^2} - 12{x^2}y + 6x{y^2} + 6xy - 2{y^3} - 7{y^2} + 12x - 12y\\
= \dfrac{{ - 749}}{8}
\end{array}$
