①21×36+36×21=36×21+21×4+21×32=21×(4+36)+21×32=21×40+21×32=21×40+21×30+21×2=21×(40+30)+42=21×70+42=1470+42=1512②72×26+36×48=2×36×26+36×48=36×52+36×48=36×(52+48)=36×100=3600楼主,你看如何?我qq82812785,欢迎各位网友与我探讨!!!!!!!