1+2+3+4·······+98+99等于多少

8+11+14+17+20+·······+305 数学计算题.呜呜呜1+2+3+4+···················+98+99+100+99+98+···············+3+2+1 1+2+3+4·······+98+99等于多少 观察下列三角形数表其中从第二行起每行的每一个数为其肩膀上两树之和则该表的最后一个数是?1 2 3 4 5 6 7 8················ 97 98 99 100 3 5 7·························· 计算1-2+3-4+5-6+······-98+99= 1 2 3 4 ·····7 ·······10 ········?1 3 5 7 ·····?······?··········290 1 4 9 ·····?······?··········? 100+99-98-97+96+95+·······+4+3-2-1怎么做? 巧算：100+99-98-97+96+95-·····+4+3-2-1 1+2+3+······+98+99+100=? 1+2+3+······+95+96+97+98+99=? 1+2+3+4+······+78+79+801/2+1/6+1/12+1/20+······+1/72+1/90100-99+98-97+96-······+4-3+2-11000-1-2-3-4-······-78-79-801/15+2/15+······+13/15+14/15注：例 1/15 就是 十五分之一 急·····················1+2+3+...+999=? (1+3+5+7+·····+99+101)—(2+4+6+8+····+98+100) 怎样快速算出1+2+3+4+5······+98+99+100? 1x2+2x3+3x4+4x5+······98x99+99x100=? 1+2-3+4+5-6······+97+98-99的解题方法是巧算快 (2+4+6+8+······+100)—(1+3+5+7+······+99)等于几 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,······.5非学无以广才,······.6······,福兮祸之所伏.7项庄舞剑,······.8······,人以群 计算1-2+3-4+5-6+······+99-100=