Đáp án:
$\begin{array}{l}
1)\left( {x + y} \right)\left( {{x^2} + 2xy + {y^2}} \right)\\
= \left( {x + y} \right){\left( {x + y} \right)^2}\\
= {\left( {x + y} \right)^3}\\
= {x^3} + 3{x^2}y + 3x{y^2} + {y^3}\\
2)\left( {x - y} \right)\left( {{x^2} - 2xy + {y^2}} \right)\\
= \left( {x - y} \right).{\left( {x - y} \right)^2}\\
= {\left( {x - y} \right)^3}\\
= {x^3} - 3{x^2}y + 3x{y^2} - {y^3}\\
3)\left( {x + y} \right)\left( {{x^2} - xy + {y^2}} \right)\\
= {x^3} + {y^3}\\
4)\left( {x - y} \right)\left( {{x^2} + xy + {y^2}} \right)\\
= {x^3} - {y^3}
\end{array}$