3a³-a²+2a-4=(3a³-3)-(a²-2a+1)
=3(a³-1)-(a-1)²
=3(a-1)(a²+a+1)-(a-1)²
=3(a-1)(a²+a+1-a/3+1/3)
=3(a-1)(a²+2a/3+4/3)
=(a-1)(3a²+2a+4)
3a³-a²+2a-4=(3a³-3)-(a²-2a+1)
=3(a³-1)-(a-1)²
=3(a-1)(a²+a+1)-(a-1)²
=3(a-1)(a²+a+1-a/3+1/3)
=3(a-1)(a²+2a/3+4/3)
=(a-1)(3a²+2a+4)