\(\left\{{}\begin{matrix}x+y+z=3\left(2\right)\\x+2y-z=2\left(1\right)\\x+yz+zx\left(2\right)\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2x+3y=5\\2z-y=1\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2x+3y=5\\10z-5y=5\end{matrix}\right.\Rightarrow2x+3y-10z+5y=0\Rightarrow2x+8y=10z\Rightarrow x+4y=5z\)tối tớ về lm tiếp