The correct option is C none of these
I3(m−n)3+m3(n−1)3+n3(I−m)3=I3[(m)3−(n)3−I(mn)(m−n)]+m3(n)3−(1)3−3(x)(x−1)+n3(I)3−(m)3(mI)(I−m)=I3[m3−n3−3mn(m−n)]+m3[n3−1−3n(n−1)]+n3[I3−m3−3mI(I−m)]=m3I3−n3I3−3m2nI3+3mn2I2+m3n3−m3−3n2m3+3nm3+n3I3−nm3−3mI2n3+3m2n3