1. 2х²-8 = 2(х²-4) = 2(х-2)(х+2)

2. 81+к⁴ = (9-к²)(9+к²) = (3-к)(3+к)(9+к²)

3. а³-4ba²+4ab² = a(a²-4ba+4b) = a(a-2b)²

4. 9x³y-12x²y²+4xy³= xy(9x²-12xy+4y²) = xy(3x-2y)²

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