当x分别等于 1 2005 , 1 2004 , 1 2003 , 1 2002 , 1 2001 , 1 2000 ,

1个回答

  • x 2

    1+ x 2 =

    1

    1

    x 2 +1 …(1)

    x 2

    1+ x 2 = 1-

    1

    1+ x 2 …(2)

    当x分别等于

    1

    2005 ,

    1

    2004 ,

    1

    2003 ,

    1

    2002 ,

    1

    2001 ,

    1

    2000 时,代入(1)式并相加得:

    1

    2005 2 +1 +

    1

    2004 2 +1 +

    1

    2003 2 +1 +

    1

    2002 2 + 1 +

    1

    2001 2 +1 +

    1

    2000 2 +1 …(3)

    当x分别等于2000,2001,2002,2003,2004,2005时,代入(2)式并相加得: 1-

    1

    1+ 2000 2 +1-

    1

    1+ 2001 2 +1-

    1

    1+ 2002 2 +1-

    1

    1+ 2003 2 +1-

    1

    1+ 2004 2 +1-

    1

    1+ 2005 2 …(4)

    将(3)式和(4)式相加得:6.

    故答案为:6.