A cura di: Alfredo Bochicchio

$4a^5-4a-8a^4+8$
$4a(a^4-1)-8(a^4-1)$
$(4a-8)(a^4-1)$
$4(a-2)(a^2+1)(a^2-1)$
$4(a-2)(a^2+1)(a+1)(a-1)$