\(\left\{{}\begin{matrix}x.y=100\\\left(x-1\right)\left(y+5\right)=100\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=100:x\\\left(x-1\right)\left(\left(100:x\right)+5\right)\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x=5\\y=20\end{matrix}\right.\)
N0 (x;y) của hệ là:(5;20)