Phân tích 

a ) \(x^2-2x-4y^2-4y\)

d ) \(x^2+y^2-x^2y^2+xy-x-y\)

c ) \(x^4+2x^3+2x^2+2x+1\)

b ) \(x^3-4x^2+12x-27\)

Phân tích nhân tử : 

a ) \(\left(ab-1\right)^2+\left(a+b\right)^2\)

\(\left[\frac{1}{\left(2x-y\right)^2}+\frac{2}{4x^2-y^2}+\frac{1}{\left(2x+y\right)^2}\right].\frac{4x^2+4xy+y^2}{16x}\)

\(\frac{4xy}{y^2-x^2}:\left(\frac{1}{x^2+2xy+y^2}-\frac{1}{x^2-y^2}\right)=\)