\(\begin{cases}x-y=3\\x^3-y^3=27\end{cases}\\↔\begin{cases}x-y=3\\(x-y)(x^2+xy+y^2)=27\end{cases}\\↔\begin{cases}x-y=3\\x^2+xy+y^2=9\end{cases}\\↔\begin{cases}x^2-2xy+y^2=9(1)\\x^2+xy+y^2=9(2)\end{cases}\)
Lấy (1)-(2) \(→x^2-2xy+y^2-x^2-xy-y^2=9-9\\↔-3xy=0\\↔\left[\begin{array}{1}x=0\\y=0\end{array}\right.\\→\left[\begin{array}{1}y=-3\\x=3\end{array}\right.\)
Vậy hệ pt có nghiệm \( (x;y)=\{(0;-3);(3;0)\}\)
