Hướng dẫn trả lời:
$\text{$64x^{4}$ + 1.}$
$\text{= ($64x^{4}$ + $16x^2$ + 1) - $16x^2$.}$
$\text{= [$(8x^2)^{2}$ + $2.8x^2.1$ + $1^2$] - $(4x)^2$.}$
$\text{= $(8x^2 + 1)^{2}$ - $(4x)^2$.}$
$\text{= [($8x^2 + 1$) + 4x].[($8x^2$ + 1) - 4x].}$
$\text{= [($8x^2$ + 4x + 1).($8x^2$ - 4x + 1).}$