题目没问题？1/(x-1)x=1/(x-1)-1/x1/x(x+1)=1/x-1/(x+1)1/（x-1)(x+2）=1/3(1/(x-1)-1/(x-2))1/(x-1)(x+3)=1/4(1/(x-1)-1/(x+3))就是裂项的思想每个这样的分数都可以拆成两个分数的差
看起来好麻烦- -
i don't know.
