很高兴回答此题。310*21*19=310(20+1)(20-1) =310(400-1) =124000-310 =123690
310×21×19 =310x(21×19) =123690
310x21x19=310x(20+1)x(20-1)=(6200+310)x(20-1)=130200-6510=123690