5а²+20а+20=5(a²+4a+4)=5(a+2)²

х-у-2х²+2у²=(x-y)-2(x²-y²)=(x-y)-2(x-y)(x+y)=(x-y)(1-2x-2y)

2)х-у-2х^2+2у^2=(х-y)-2(х^2-y^2)=(х-y)((х+y)-2)

1) 5 а^2+20а+20=5a^2+10а+10а+20=5а(а+2)+10(2+а)=(2+а)(5а+10)