2⁢RG⁡(x+λ,y+λ,z+λ)+2⁢RG⁡(x+μ,y+μ,z+μ)=2⁢RG⁡(x,y,z)+λ⁢RF⁡(x+λ,y+λ,z+λ)+μ⁢RF⁡(x+μ,y+μ,z+μ)+λ+μ+x+y+z.