1/（x+1）(x+2) + 1/(x+2)(x+3)+.+1/(x+1994)(x+1995)=2x+3987/3x+59851/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)...+1/(x+1994)-1/(x+1995)=2x+3987/3x+5985 (这一步是计算中常用的方法,可以把项依次销掉)1/(x+1)-1/(x+1995)...