Giải thích các bước giải:
Ta có:
\[\begin{array}{l}
A = \left( {x + 1} \right)\left( {x + 2} \right)\left( {x + 3} \right)\left( {x + 4} \right) - 24\\
= \left[ {\left( {x + 1} \right)\left( {x + 4} \right)} \right]\left[ {\left( {x + 2} \right)\left( {x + 3} \right)} \right] - 24\\
= \left( {{x^2} + 5x + 4} \right)\left( {{x^2} + 5x + 6} \right) - 24\\
= \left[ {\left( {{x^2} + 5x + 5} \right) - 1} \right]\left[ {\left( {{x^2} + 5x + 5} \right) + 1} \right] - 24\\
= {\left( {{x^2} + 5x + 5} \right)^2} - 25\\
= \left( {{x^2} + 5x} \right)\left( {{x^2} + 5x + 10} \right)\\
= x\left( {x + 2} \right)\left( {{x^2} + 5x + 10} \right) \vdots x
\end{array}\]
