a³+a²-3a-2
=a³+a²-2a-a-2
=a(a²+a-2)-(a+2)
=a(a-1)(a+2)-(a+2)
=(a+2)(a²-a-1)
=(a+2)[(a-1/2)²-5/4]
=(a+2)(a-1/2-√5/2)(a-1/2+√5/2)
a³+a²-3a-2
=a³+a²-2a-a-2
=a(a²+a-2)-(a+2)
=a(a-1)(a+2)-(a+2)
=(a+2)(a²-a-1)
=(a+2)[(a-1/2)²-5/4]
=(a+2)(a-1/2-√5/2)(a-1/2+√5/2)