\(x+y+100=0\)
\(\Leftrightarrow\)\(x+y=-100\)(1)
\(x-y=0\) (2)
Từ (1) và (2) suy ra:
\(\left(x+y\right)+\left(x-y\right)=-100\)
\(\Leftrightarrow\)\(2x=-100\)
\(\Leftrightarrow\)\(x=-100\div2=-50\)
\(\Rightarrow\)\(y=-100+50=-50\)
Vậy \(x=y=-50\)
\(\hept{\begin{cases}x+y+100=0\\x-y=0\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}x=y\\y+y+100=0\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}x=y\\2y=-100\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}y=-50\\x=-50\end{cases}}\)
vậy \(\hept{\begin{cases}x=-50\\y=-50\end{cases}}\)
