a) x^2 - 2x - 4y^2 - 4y
= (x - 2y)(x + 2y) - 2(x + 2y)
= (x + 2y)(x - 2y - 2)
b)x^4+2x^3-4x-4
= (x^2 - 2)(x^2 + 2) + 2x(x^2 - 2)
= (x^2 - 2)(x^2 + 2x + 2)
c)x^2(1-x^2)-4-4x^2
= x^2 ( 1 - x^2) - 4 ( 1 - x^2)
= (x^2 - 2^2 ) ( 1 - x^2)
= ( x - 2 ) ( x + 2) ( 1 - x ) ( 1 + x)
d)(1+2x)(1-2x)-x(x+2)(x-2)
= 1 - 4x^2 - x(x^2 - 2^2)
= 1 - 4x^2 - x^3 + 2x^2
= 1 - 2x^2 - x^3
e)x^2+y^2-x^2 y^2+xy-x-y