5000-1-2-3-······-76-77-78=?

1+2++3+··········+10000= 1+2+3+4··· ···+78+79=? 计算：（-78）+（-77）+（-76）+（-75）+······+100=? 1/3+2/3=1,但0.333···+0.666···=0.999···,为神马?额······谁能解释一下····· 1+2+3+4+······+78+79+80 俗语和名句的填空1······,自知之明.2······,行必果.3工欲善其事,······.4临渊羡鱼,······. 1、2······· (1-2)×(2-3)×(3-4)×······×(19-20)= 1!+2!+3!·····n! 公式 1\(2\3)\(3\4)······\(18\19)\(19\20)= 1+2+3+4+5+6······38+39=? 1+2+3+······+98+99+100=?