2.
a) 18ab³-2a³b=2ab(9b²-a²)=2ab(3b-a)(3b+a)
б) a⁴+6a²b+9b²=(a²+3b)²=(a²+3b)(a²+3b)
3.
2(5-y²)(y²+5)+(y²-3)²-(y²+y-1)(4-y²)=y³-11y²-4y+63
1) 2(5-y²)(y²+5)=2(5-y²)(5+y²)=2(25-y⁴)=50-2y⁴
2) (y²-3)²=y⁴-6y²+9
3) (y²+y-1)(4-y²)=4y²+4y-4-y⁴-y³+y²=-y⁴-y³+5y²+4y-4
4) 50-2y⁴+y⁴-6y²+9+y⁴+y³-5y²-4y+4=y³-11y²-4y+63