｜1/2001-1/2000｜+｜1/2000-1/1999｜-｜1/1999-1/2001｜=?1/2+1/4+1/8+...+1/256+1/512+1/1024=?1+2+3+...+1997+1998+1999=?

｜1/2001-1/2000｜+｜1/2000-1/1999｜-｜1/1999-1/2001｜=?1/2+1/4+1/8+...+1/256+1/512+1/1024=?1+2+3+...+1997+1998+1999=?
｜1/2001-1/2000｜+｜1/2000-1/1999｜-｜1/1999-1/2001｜=?
1/2+1/4+1/8+...+1/256+1/512+1/1024=?
1+2+3+...+1997+1998+1999=?

｜1/2001-1/2000｜+｜1/2000-1/1999｜-｜1/1999-1/2001｜=?1/2+1/4+1/8+...+1/256+1/512+1/1024=?1+2+3+...+1997+1998+1999=?
=1/2000-1/2001+1/1999-1/2000+1/2001-1/1999
=0
=1/2+1/4+1/8+...+1/256+1/512+1/1024+1/1024-1/1024
=1/2+1/4+1/8+...+1/256+1/512+1/512-1/1024
=...
=1-1/1024
=1023/1024
=(1+1999)*1999/2
=2000/2*1999
=1000*1999
=1999000

（1）原式=1/2000-1/2001+1/1999-1/2000-（1/1999-1/2001）
=1/2000-1/2001+1/1999-1/2000-1/1999+1/2001
=0
（2）原式=（1-1/2）+（1/2-1/4）+（1/4-1/8）……+（1/512-1/1024）
=1-1/1024
=1023/1024
（3）原式=（1+1999）*1999/2=1999000

｜1/2001-1/2000｜+｜1/2000-1/1999｜-｜1/1999-1/2001｜=0
1\2+1\4+1\8+...+1\256+1\512+1\1024
＝1\2+1\4+1\8+...+1\256+1\512+1\1024+1\1024－1\1024
=1-1/1024
=1023/1024
1+2+3+...+1997+1998+1999
=(1+1999)+(2+1998)+(3+1997)+...+(999+1001)+1000
=1998000+1000
=1999000

(3)(1+1999)+(2+1998)+(3+1997)+...+(999+1001)+1000=2001000