ĐKXĐ: ...
\(\sqrt{12y-x^2y}=12-x\sqrt{12-y}\)
\(\Rightarrow12y-x^2y=144+12x^2-x^2y-24x\sqrt{12-y}\)
\(\Leftrightarrow x^2-2x\sqrt{12-y}+12-y=0\)
\(\Leftrightarrow\left(x-\sqrt{12-y}\right)^2=0\Rightarrow x=\sqrt{12-y}\)
\(\Rightarrow y=12-x^2\)
Thay vào pt (1):
\(3x^2-x+3=\sqrt{3x+1}+\sqrt{5x+4}\)
\(\Leftrightarrow3x^2-3x+\left(x+1-\sqrt{3x+1}\right)+\left(x+2-\sqrt{5x+4}\right)=0\)
\(\Leftrightarrow3\left(x^2-x\right)+\frac{x^2-x}{x+1+\sqrt{3x+1}}+\frac{x^2-x}{x+2+\sqrt{5x+4}}=0\)
\(\Leftrightarrow...\)
