求2道计算题,一：9+99+999+9999 二：998+997+996+1002+1003+1004 = = = =

1、原式=10-1+100-1+1000-1+10000-1=11110-4=11106
2、原式=998+1002+997+1003+996+1004=2000+2000+2000=6000

9+99+999+9999
=10-1+100-1+1000-1+1000-1
=11110-4
=11106
二：
998+997+996+1002+1003+1004
=1000-2+1000-3+1000-4+1000+2+1000+3+1000+4
=6000

9+99+999+9999
=100+1000+10000+6
=11106
998+997+996+1002+1003+1004
=（998+1002）+（997+1003）+（996+1004）
=2000+2000+2000
=6000

(1)9+99+999+9999
=10-1+100-1+1000-1+10000-1
=11110-4
=11106
(2)998+997+996+1002+1003+1004
=(998+1002)+(997+1003)+(996+1004)
=2000+2000+2000
=6000

9+99+999+9999
=1+9+1+99+1+999+1+9999-4
=11110-4
=11106
二：
998+997+996+1002+1003+1004
=(998+1002)+(997+1003)+(996+1004)
=2000+2000+2000
=6000

一：9+99+999+9999
=6+100+1000+10000
=11106
二：998+997+996+1002+1003+1004
=998+1002+997+1003+996+1004
=2000+2000+2000
=6000