A²+2ab+b²-c²+2cd-d²=(a+b)²-(c-d)²=(a+b-c+d)(a+b+c-d)
a⁶-a⁴+2a³+2a²=a⁴(a²-1)+2a²(a+1)=a⁴(a-1)(a+1)+2a²(a+1)=
=a²(a+1)(a²(a-1)+2)=a²(a+1)(a³-a²+2)=a²(a+1)(a³+a²-2a²-2a+2a+2)=
=a²(a+1)(a²(a+1)-2a(a+1)+2(a+1))=a²(a+1)²(a²-2a+2)
c⁵-c⁴-c+1=c⁴(c-1)-(c-1)=(c-1)(c⁴-1)=(c-1)(c²-1)(c²+1)=
=(c-1)²(c+1)(c²+1)