The original formula = ∫∫∫ (on tetrahedron) (y+z+x)dv is obtained by Gaussian formula.
=∫(0 to 1)dx∫(0 to 1-x)dy∫(0 to 1-x-y) (x+y+z)dz
Product result =3/40.
20 18 Meizhou senior high school entrance examination total score: 1040 Meizhou adjusted the senior high school entrance