Đáp án:
$\begin{array}{l}
2)\left( {x - 3} \right)\left( {x + 3} \right) - {\left( {x - 2} \right)^2} = 1\\
\Leftrightarrow {x^2} - 9 - \left( {{x^2} - 4x + 4} \right) = 1\\
\Leftrightarrow {x^2} - 9 - {x^2} + 4x - 4 = 1\\
\Leftrightarrow 4x = 14\\
\Leftrightarrow x = \dfrac{7}{2}\\
Vậy\,x = \dfrac{7}{2}\\
3)\left( {x - 1} \right)\left( {{x^2} + x + 1} \right) - x\left( {{x^2} + 2} \right) - 4 = 0\\
\Leftrightarrow {x^3} - 1 - {x^3} - 2x - 4 = 0\\
\Leftrightarrow 2x = - 5\\
\Leftrightarrow x = - \dfrac{{52}}{{}}\\
Vậy\,x = - \dfrac{5}{2}\\
4)x\left( {x - 5} \right)\left( {x + 5} \right) - \left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right) = 3\\
\Leftrightarrow x\left( {{x^2} - 25} \right) - \left( {{x^3} + {2^3}} \right) = 3\\
\Leftrightarrow {x^3} - 25x - {x^3} - 8 = 3\\
\Leftrightarrow 25x = - 11\\
\Leftrightarrow x = - \dfrac{{11}}{{25}}\\
Vậy\,x = - \dfrac{{11}}{{25}}
\end{array}$
