这是道计算题,
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这是道计算题,这是道计算题,这是道计算题,2/(x+1)(x+3)+2/(x+3)(x+5)+.2/(x+1997)(x+1999)=1/(x+1)-1/(x+3)+1/(x+3)-1/(x+5)+1
这是道计算题,
这是道计算题,
这是道计算题,
2/(x+1)(x+3)+2/(x+3)(x+5)+.2/(x+1997)(x+1999)
=1/(x+1)-1/(x+3)+1/(x+3)-1/(x+5)+1/(x+5)-.-1/(x+1997)+1/(x+1997)-1/(x+1999)
=1/(x+1)-1/(x+1999)
=(x+1999-x-1)/(x+1)(x+1999)
=1998/(x+1)(x+1999)