1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+1998)(x+1999),当x=1时,求该代数式的值

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1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+1998)(x+1999),当x=1时,求该代数式的值
1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+1998)(x+1999),当x=1时,求该代数式的值

1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+1998)(x+1999),当x=1时,求该代数式的值
1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+1998)(x+1999)
=[1/x-1/(x+1)]+[1/(x+1)-1/(x+2)]+[1/(x+2)-1/(x+3)]+.+[1/(x+1998)-1/(x+1999)]
=1-1/(x+1999)
=1-1/2000
=1999/2000