596+597+598+599+600+601+602
=596+597+(598+602)+(599+601)+600
=(600-4)+(600-3)+1200+1200+600
=600-4+600-3+1200+1200+600
=1200+1200+1200+600-7
=4200-7
=4193
原式=599*7=(600-1)*7=4200-7=4193
原式
=599x7
=600x7-7
=4200-7
=4193
(600-4)+(600-3)+(600-2)+(600-1)+600+(600+1)+(600+2)=7×600-2-1+1+2=4200