1*2+2*3+3*4+···100*101怎么做?

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 怎样计算1×2+2×3+3×4+······+100×101 1 2 3 4 ·····7 ·······10 ········?1 3 5 7 ·····?······?··········290 1 4 9 ·····?······?··········? 计算1-2+3-4+5-6+······+99-100= 计算（+1）+(-2)+(+3)+(-4)+······+（-100）+(+101)+(-102) 计算：(2+4+6+8+···+100)-(1+3+5+···+99) 1+2+3+4+5······+100+101=几 1+2+3+4+5+······+100（用简便算法） (2+4+6+8+······+100)—(1+3+5+7+······+99)等于几 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·························· 有一组数,1/1,1/2,2/2,1/3,2/3,3/4,4/4······1/100,2/100,······求和 1+（-2）+3+（-4）···········+99-100等于多少 巧算：100+99-98-97+96+95-·····+4+3-2-1 证明1·3·5·····(2n-1)/2·4·6·····2n 急·····················1+2+3+...+999=? 100+99-98-97+96+95+·······+4+3-2-1怎么做? 负1加2减3加4减5加·······加100 2[4/3y—（2/3y—1/2）]=3/4y急·································!1