原式=(2001+2000-1999-1998)+(1997+1996-1995-1994)+...+(5+4-3-2)+1
=4×(2001-1)÷4+1
=2001
1-2-3+4+5-6-7+8+9-10……+-1999+2000+2001=?
1-2-3+4+5-6-7+8+9-10……+-1999+2000+2001=?
数学人气:204 ℃时间:2020-06-04 06:53:27
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