Giải thích các bước giải:
$\begin{array}{l}
a){(2x + 1)^2} + {(2x - 1)^2} - 2(2x + 1)(2x - 1)\\
= {\left( {2x + 1 - \left( {2x - 1} \right)} \right)^2}\\
= {2^2}\\
= 4\\
b)2{x^3} - 3{x^2} + 6x - 9\\
= {x^2}\left( {2x - 3} \right) + 3\left( {2x - 3} \right)\\
= \left( {2x - 3} \right)\left( {{x^2} + 3} \right)\\
\Rightarrow \left( {2{x^3} - 3{x^2} + 6x - 9} \right) \vdots \left( {2x - 3} \right) = {x^2} + 3
\end{array}$
Vậy $\left( {2{x^3} - 3{x^2} + 6x - 9} \right) \vdots \left( {2x - 3} \right) = {x^2} + 3$
