\(x^3+y^3+x+y\)
\(=\left(x^3+y^3\right)+\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)+\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2+1\right)\)
$#flo$
`x^3 + y^3 + x + y`
`=(x + y)(x^2 - xy + y^2) + (x + y)`
`= (x + y)(x^2 - xy + y^2 + 1)`
\(x^3+y^3+x+y\\ =\left(x+y\right)\left(x^2+xy+y^2\right)+xy\\ =\left(xy\right)\left(x^2+xy+y^2+1\right)\)