1.
(а-3)²=а² - 6а+9
(2х+у)²=4х²+4ху+у²
(5b-4x)(5b+4x)=25b² - 16x²
2.
4a(a-2)-(a-4)²=4a²-8a-a²+8a-16=3a² - 16
ab² - ac²=a(b²-c²)=a(b-c)(b+c)
-3a² - 6ab - 3b²= -3(a²+2ab+b²)= - 3(a+b)(a+b)
3.
(y²-2y)² -y²(y+3)(y-3)+2y(2y²+5)=y^4 - 4y³+4y² - y^4+9y²+4y³ +10y=13y² +10y=y(13y+10)
4.
25a² -(a+3)²=(5a-a-3)(5a+a+3)=(4a-3)(6a+3)=3(4a-3)(2a+1)
27a³+b³=(3a+b)(9a² -3ab+b²)
16x^4 -81=(4x²-9)(4x²+9)=(2x-3)(2x+3)(4x²+9)
x² - x - y² - y=(x²-y²) -(x+y)=(x-y)(x+y) - (x+y)=(x+y)(x-y-1)