Tìm x biết: 9x (x-1) - (3x-1)^2 =11

* Hướng dẫn giải

$\begin{array}{l}9\mathrm{x}\left(\mathrm{x}-1\right)-{\left(3\mathrm{x}-1\right)}^2=11\\ 9{\mathrm{x}}^2-9\mathrm{x}-9{\mathrm{x}}^2+6\mathrm{x}-1=11\\ -3\mathrm{x}=12\Rightarrow \mathrm{x}=-4\end{array}$