1
(x²+2x+1)-(9y²-12y+4)=(x+1)²-(3y-2)²=(x+1-3y+2)(x+1+3y-2)=
=(x-3y+3)(x+3y-1)
2
(x²+4x+4)-(4y²-4y+1)=(x+2)²-(2y-1)²=(x+2-2y+1)(x+2+2y-1)=
=(x-2y+3)(x+2y+1)
3
(a²b²+2ab+1)-(c²+8c+16)=(ab+1)²-(c+4)²=(ab+1-c-4)(ab+1+c+4)=
=(ab-c-3)(ab+c+5)
4
(9a²-12a+4)-(a²-2ab+b²)=(3a-2)²-(a-b)²=(3a-2-a+b)(3a-2+a-b)=
=(2a+b-2)(4a-b-2)