https://i.imgur.com/h9XKJLc.jpg
*Ta có :
\(\left|x-y+3\right|+\left(2x+3y-4\right)^2+\sqrt{x+y+z}\ge0\) (3 biểu thức đều không âm)
\(\Rightarrow\)\(\left|x-y+3\right|=\left(2x+3y-4\right)^2=\sqrt{x+y+z}=0\)
\(\Rightarrow\)\(\left|x-y+3\right|=\left(2+3-4.\left[x.y\right]\right)^2=\sqrt{x+y+z}\)
\(\Rightarrow\)\(\left|x-y+3\right|=\left(1.\left[x.y\right]\right)^2=\sqrt{x+y+z}\)
\(\Rightarrow\)\(\left|x-y+3\right|=\left[x.y\right]=\sqrt{x+y+z}\)
\(\Rightarrow\)tịt(hết ý)