1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=

来源:学生作业帮助网 编辑:六六作业网 时间:2024/11/22 20:16:18
1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+

1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=
1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=

1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=
1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1
=(1994-1993)+1992+(1991-1990)+1989+...+6+(5-4)+3+(2-1)
=(3+6+9+...+1989+1992)+[(1994-664)/2]
=[664(3+1992)/2]+665
=662340+665=663005

(1994-1993)+(1992-1991)+……+(2-1)=1+1+1+1+……+1【共997个1】=997