a: \(x^4+2x^3+3x^2+2x+1\)

\(=x^4+x^3+x^2+x^3+x^2+x+x^2+x+1\)

\(=x^2\left(x^2+x+1\right)+x\left(x^2+x+1\right)+\left(x^2+x+1\right)\)

\(=\left(x^2+x+1\right)\left(x^2+x+1\right)=\left(x^2+x+1\right)^2\)

b: \(x^4-4x^3+2x^2+4x+1\)

\(=x^4-2x^3-x^2-2x^3+4x^2+2x-x^2+2x+1\)

\(=x^2\left(x^2-2x-1\right)-2x\left(x^2-2x-1\right)-\left(x^2-2x-1\right)\)

\(=\left(x^2-2x-1\right)\left(x^2-2x-1\right)=\left(x^2-2x-1\right)^2\)

c: \(x^4+x^3+2x^2+2x+4\)

\(=x^4-x^3+2x^2+2x^3-2x^2+4x+2x^2-2x+4\)

\(=x^2\left(x^2-x+2\right)+2x\left(x^2-x+2\right)+2\left(x^2-x+2\right)\)

\(=\left(x^2-x+2\right)\left(x^2+2x+2\right)\)

a: \(3x^3y^2-12x^2y^3\)

\(=3x^2y^2\cdot x-3x^2y^2\cdot4y\)

\(=3x^2y^2\left(x-4y\right)\)

b: \(x^2-5x+xy-5y\)

=x(x-5)+y(x-5)

=(x-5)(x+y)

d: \(2x^2-4xy+2y^2-18\)

\(=2\left(x^2-2xy+y^2-9\right)\)

\(=2\left\lbrack\left(x-y\right)^2-3\right\rbrack\)

=2(x-y-3)(x-y+3)

e: \(x^3-2020x_{}^2+2020x-2019\)

\(=x^3-x^2+x-2019x^2+2019x-2019\)

\(=x\left(x^2-x+1\right)-2019\left(x^2-x+1\right)=\left(x^2-x+1\right)\left(x-2019\right)\)

a) \(x^2-2x-4y^2-4y=\left(x^2-4y^2\right)-\left(2x+4y\right)=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)=\left(x+2y\right)\left(x-2y-2\right)\)

b) \(x^3+2x^2+2x+1=\left(x+1\right)\left(x^2-x+1\right)+2x\left(x+1\right)=\left(x+1\right)\left(x^2-x+1+2x\right)=\left(x+1\right)\left(x^2+x+1\right)\)

c) \(x^3-4x^2+12x-27=x^3-3x^2-x^2+3x+9x-27=x^2\left(x-3\right)-x\left(x-3\right)+9\left(x-3\right)=\left(x-3\right)\left(x^2-x+9\right)\)

d) \(a^6-a^4+2a^3+2a^2=a^2\left(a^4-a^2+2a+2\right)=a^2\left[a^2\left(a-1\right)\left(a+1\right)+2\left(a+1\right)\right]=a^2\left(a+1\right)\left(a^3-a^2+2\right)=a^2\left(a+1\right)\left[a^3+a^2-2a^2+2\right]=a^2\left(a+1\right)\left[a^2\left(a+1\right)-2\left(a-1\right)\left(a+1\right)\right]=a^2\left(a+1\right)^2\left(a^2-2a+2\right)\)

a) Ta có: \(x^2-2x-4y^2-4y\)

\(=\left(x^2-4y^2\right)-\left(2x+4y\right)\)

\(=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)\)

\(=\left(x+2y\right)\left(x-2y-2\right)\)

b) Ta có: \(x^3+2x^2+2x+1\)

\(=\left(x^3+1\right)+2x\left(x+1\right)\)

\(=\left(x+1\right)\left(x^2-x+1\right)+2x\left(x+1\right)\)

\(=\left(x+1\right)\left(x^2+x+1\right)\)

a) (x - y)(x + y + 3).                    b) (x + y - 2xy)(2 + y + 2xy).

c) x 2 (x + l)( x 3  -  x 2  + 2).              d) (x – 1 - y)[ ( x   -   1 ) 2   +   ( x   -   1 ) y   +   y 2 ].