简便计算:9999×9999+19999
=1999+9999*(10000-1)
=1999+9999*10000-9999
=99990000+1999-9999
=99990000-8000
=99982000
1999+9999×9999
=1999+9999×(10000-1)
=1999+99990000-9999
=99990000-(10000-1)+1999
=99990000-10000+2000
=99980000+2000
=99982000
1999+9999×9999
=2000-1+(10000-1)(10000-1)
=2000-1+100000000-20000+1
=100000000