1x2十2x3十3x4公式推导
双言版37801x2十2x3十3x4十…...十1o0x101 -
施虾狠19557718297 ______[答案] 应用公式 1+2+3+.+n=1/2*n(n+1) 1^2+2^2+3^2+...+n^2=1/6n(n+1)(2n+1) 1x2十2x3十3x4十…...十100x101 =1x(1+1)十2x(2+1)十3x(3+1)十…...十100x(100+1) =(1^2+2^2+3^2+.+100*2)+(1+2+3+...+100) =1/6*100*101*201+1/2*101*100 =1/6*10100(201+...
双言版37801x2+2x3+3x4+4x5+.....+n(n+1)等于多少?急救!! -
施虾狠19557718297 ______ 1x2+2x3+3x4+…+n(n+1) =1^2+1+2^2+2+3^2+3+…+n^2+n =(1^2+2^2+3^2+…+n^2)+(1+2+3+…+n) =1/6*n(n+1)(2n+1)+1/2*n(n+1) =1/6*n(n+1)(2n+1+3)(提取公因式) =1/3*n(n+1)(n+2)
双言版37801x2+2x3+3x4+......+100x101= -
施虾狠19557718297 ______ 1x2+2x3+3x4+......+100x101= 的通项公式An=n*(n+1)=n²+n 前n项和Sn=(1²+2²+……+n²)+(1+2+……+n) =n(n+1)(2n+1)/6+n(n+1)/2 所以 1x2+2x3+3x4+......+100x101=S(100) =100*101*201/6+100*101/2=343400 前项平方和公式为1²+2²+……+n²=n(n+1)(2n+1)/6 推导过程见http://wenwen.sogou.com/z/q655520554.htm?si=2
双言版37801x2+2x3+3x4+...+10x11=? -
施虾狠19557718297 ______ 展开全部1x2+2x3+3x4+...+10x11=2+6+12+20+30+42+56+72+90+110=440
双言版37801x2+2x3+3x4+···+10x11 -
施虾狠19557718297 ______ 1*2=1*3(1*2*3-0*1*2)2*3=1/3(2*3*4-1*2*3)...............10*11=1/3(10*11*12-9*10*11) 所以1x2+2x3+3x4+···+10x11=1/3(10*11*12-0*1*2)=440
双言版37801x2+2x3+3x4+4x5+5x6+6x7+7x8+......+nx(n+1) 要公式,别搞太深奥!! -
施虾狠19557718297 ______ 先求它们的倒数和,再把结果倒回来. 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11 =10*(10+1)*(10+2)÷3 =10*11*12÷3 =110*12÷3 =1320÷3 =440
双言版37801x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9= -
施虾狠19557718297 ______ 1x2 + 2x3 + 3x4 + ...... + n(n+1) = 1/3 * n(n+1)(n+2) 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9 = 1/3 * 8 * 9 * 10 = 240
双言版37801x2十2x3十3x4十4x5十5x6 , -
施虾狠19557718297 ______[答案] 1x2十2x3十3x4十4x5十5x6 = 2 + 6+12+20+30 = 70 无量寿佛,佛说苦海无涯回头是岸! 施主,我看你骨骼清奇,器宇轩昂,且有慧根,乃是万中无一的武林奇才. 潜心修习,将来必成大器,吾手中正好有一本宝典,欲赠于施主 鄙人有个小小的考验...
双言版37801x2十2x3十3x4十......十99x100推算过程 -
施虾狠19557718297 ______ 1 - 1/2+1/2 - 1/3+1/3 - 1/4+1/4 - 1/5+……+1/98 - 1/99+1/99 - 1/100=1 - 1/100=99/100
双言版37803(1x2十2x3十3x4…十2011x2012)怎么计算? -
施虾狠19557718297 ______[答案] n(n+1)=n²+n 原式=3(1²+1+2²+2+……+2011²+2011) =3(1²+2²+3²+……2011²+1+2+3+.2011) 1+2+3+n=n(n+1)/2 1²+2²+3²+……n²=n*(n+1)*(2n+1)/6 带入,原式的值可求