\(x^2+xy\left(2y-1\right)=2y^3-2y^2-x\)
\(\Leftrightarrow x^2+x\left(2y^2-y+1\right)-\left(2y^3-2y^2\right)=0\)
\(\Delta=\left(2y^2-y+1\right)^2+4\left(2y^3-2y^2\right)=\left(2y^2+y-1\right)^2\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-\left(2y^2-y+1\right)-\left(2y^2+y-1\right)}{2}=-2y^2\le0\left(loại\right)\\x=\dfrac{-\left(2y^2-y+1\right)+2y^2+y-1}{2}=y-1\end{matrix}\right.\)
Thế xuống dưới:
\(6\sqrt{x-1}+x+8=4x^2\)
\(\Leftrightarrow4x^2-x-14-6\left(\sqrt{x-1}-1\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(4x+7\right)-\dfrac{6\left(x-2\right)}{\sqrt{x-1}+1}=0\)
\(\Leftrightarrow\left(x-2\right)\left(4x+7-\dfrac{6}{\sqrt{x-1}+1}\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(4x+\dfrac{7\sqrt{x-1}+1}{\sqrt{x-1}+1}\right)=0\)
\(\Leftrightarrow x=2\)
