Question 1020445
{{{(x+y+z)^3 - x^3 - y^3 - z^3}}}=
{{{(x^3+3x^2y+3x^2z+3xy^2+6xyz+3xz^2+y^3+3y^2z+3yz^2+z^3)- x^3 - y^3 - z^3}}}=
{{{3x^2y+3x^2z+3xy^2+6xyz+3xz^2+3y^2z+3yz^2}}}=
{{{3(x^2y+x^2z+xy^2+2xyz+xz^2+y^2z+yz^2)}}}=
{{{3(x^2(y+z) + y^2(x+z) + z^2(x+y) + 2xyz)}}}
This can be further factored to
{{{3(x+y)(x+z)(y+z)}}}