1+（-2）+3+（-4）+.+2003+（-2004）= (1 - 2) + (3 - 4) + ...+ (2003 - 2004)= (-1)× 1002= -1002| 1-1/2 | + | 1/2-1/3 | + | 1/3-1/4 | +.+ | 1/9-1/10 | = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ...+ 1/9 - 1/10...