2m((m-1)+(m-2)(m+2)+2m

2m((m-1)+(m-2)(m+2))+2m= 2m((m-1)+(m^2-4))+2m=2m(m-1+m^2-4)+2m=2m(m-5+m^2)+2m=2m^2-10m+2m^3+2m=2m^3+2m^2-8m