61+4×610+59×61=61+61×40+61×59=61×（1+40+59）=61×100=610099999×77778+33333×66666=99999×77778+99999×22222=99999×（77778+22222）=999990000066×21+19×21+85×19=(66+19)×21+85×19=85×21+85×19...