DKXD : y \le 1 ,3x+22 \ge xy
(1)\Leftrightarrow \sqrt{x^2+9y^2+6xy-4x-12y+8}-\sqrt{(x-y)^2+4}+2(x+y-1)=0
\Leftrightarrow \frac{4(2y-1)(x+y-1)}{\sqrt{(x+3y-2)^2+4}+\sqrt{(y-x)^2+4}}+2(x+y-1)=0
\Leftrightarrow (x+ý-1).f(x)=0
Với y \ge \frac 12 thì f(x)>0
Với y < \frac 12 thì f(x) \overset{min-cop-xki}\ge \frac{4(2y-1)}{\sqrt{(4y-2)^2+16}}+2=\frac{2y-1}{\sqrt{(2y-1)^2+4}}+2>0
Vậy (1)\Leftrightarrow y=1-x
Thế xuống pt thứ 2
\sqrt{3x-x(1-x)+22}-\sqrt x=x^2-2+2x+3
\Leftrightarrow \sqrt{x^2+2x+22}-\sqrt x=(x+1)^2
\Leftrightarrow \sqrt{x^2+2x+22}-5+1-\sqrt x=(x+1)^2-4
\Leftrightarrow \frac{(x-1)(x+3)}{\sqrt{x^2+2x+22}+5}=(x-1)(x+3)+\frac{x-1}{\sqrt x+1 }
\Leftrightarrow x=1\Leftrightarrow \begin{cases}x=1 \\ y=0 \end{cases}