\(x^3+y^3+x+y\)

\(=(x+y)(x^2-xy+y^2)+(x+y)\)

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

\(X^2y+xy^2-x-y\)
\(=xy(x+y)-(x+y)=(xy-1)(x+y)\)

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

\(=3\left(x-y\right)+\left(x-y\right)\left(x+y\right)\)

\(=\left(x-y\right)\left(x+y+3\right)\)

\(=3\left(x-y\right)+\left(x-y\right)\left(x+y\right)=\left(x-y\right)\left(x+y+3\right)\)

`x^2-y^2-3x+3y`

`=(x^2-y^2) -(3x-3y)`

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

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

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

x²+3x+3y+xy

=x(x+3)+y(3+x)

=(x+3)(x+y)

     x² + 3x + 3y + xy

=   ( x² + xy) + ( 3x + 3y)

= x( x + y) + 3 ( x + y)

= ( x + y) ( x + 3) 

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

#)Giải :

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

\(x^2-y^2+3x-3y\)

\(=\left(x-y\right)\left(x+y\right)+3\left(x-y\right)\)

\(=\left(x-y\right)\left(x+x+3\right)\)

~ Rất vui vì giúp đc bn ~