首先是个负数绝对值的话等于(1997/1998)(1996/1997)……(999/1000)=999/1998=1/2所以答案是-1/2
(1/1998 -1)(1/1997 -1)(1/1996 -1)....(1/1000 -1)=1997/1998x196/1997x1995/1996x....x999/1000=999/1998=1/2
