Ответ:

1. 2(х²-4)=2(х-2)(х+2)

2.(9-к²)(9+к²)=(3-к)(3+к)(9+к²)

3.а(а²-4аb+4b²)=a(a-2b)²

4.xy(9x²-12xy+4y²)=xy(3x-2y)²

5.(x²-1)(25x²-10x+1)=(x-1)(x+1)(5x-1)²