Question

X + y+z whole cube minus x cube minus y cube minus z cube

Answer 1

(X+y+z)^3-x^3-y^3-z^3

=

(x^3 + y^3 + z^3 + 3x^2y + 3xy^2

+ 3x^2z + 3z^2x + 3y^2z + 3z^2y + 6xyz)-x^3-y^3-z^3

=

3x^2y + 3xy^2

+ 3x^2z + 3z^2x + 3y^2z + 3z^2y + 6xyz