1)2a²-2b²-a+b=2(a²-b²)-(a-b)=2(a-b)(a+b)-(a-b)=(a-b)(2a+2b-1)
2)2x+y+y²-4x²=(2x+y)+(y²-4x²)=(2x+y)+(y-2x)(y+2x)=(y+2x)(1+y-2x)
3)a³-ab-a²b+a²=(a³-a²b)+(a²-ab)=a²(a-b)+a(a-b)=(a-b)(a²+a)=(a-b)·a·(a+1)
4)1-x²+2xy-y²=1-(x²-2xy+y²)=1-(x-y)²=(1-x+y)(1+x-y)