\(\Leftrightarrow\left\{{}\begin{matrix}x+y=60\\x-y=28\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x=88\\x-y=28\end{matrix}\right.\Leftrightarrow\left(x,y\right)=\left(44;16\right)\)
\(\left\{{}\begin{matrix}3x+3y=180\\x-y=28\end{matrix}\right.\)
đề như thế này phải ko bn?
\(\left\{{}\begin{matrix}3x+3y=180\\x-y=28\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x+3y=180\\-3x+3y=-84\end{matrix}\right.\)
cộng từng vế của 2 pt ta có:
\(\Leftrightarrow6y=96\)
\(\Leftrightarrow\left\{{}\begin{matrix}6y=96\\x-y=28\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=16\\x-16=-28\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=16\\x=-28+16\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=16\\x=-12\end{matrix}\right.\)
vậy hpt có 2 tạp nghiệm \(x=-12\) và\(y=16\)
\(\left\{{}\begin{matrix}3x+3y=180\\x-y=28\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3\left(x+y\right)=180\\x-y=28\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x+y=60\\x-y=28\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x=88\\x-y=28\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=44\\y=16\end{matrix}\right.\)
