\(x^5+y^5=\left(x^2+y^2\right)\left(x^3+y^3\right)-x^2y^3-x^3y^2\)
\(=\left(x+y\right)\left(x^2+y^2\right)\left(x^2-xy+y^2\right)-x^2y^2\left(x+y\right)\)
\(=\left(x+y\right)\left(\left(x^2+y^2\right)\left(x^2-xy+y^2\right)-x^2y^2\right)\)
\(=\left(x+y\right)\left(x^4-x^3y+x^2y^2-xy^3+y^4\right)\)