(m+mi)^6=-64im^6*(1+i)^6=-64i(1+i)^6=-8im^6=8m=±√2
4i^3是-64i,所以（m+mi)^2=4i,即m^2(1+i)^2=4i,而(1+i)^2=2i,所以m^2=2,m=根号2或者负根号2.
