1/2×4+1/3×5+1/4×6+1/5×7+……+1/8×10+1/9×11

来源：学生作业帮助网编辑：作业帮时间：2024/04/25 12:03:43

1/2×4+1/3×5+1/4×6+1/5×7+……+1/8×10+1/9×11
1/2×4+1/3×5+1/4×6+1/5×7+……+1/8×10+1/9×11

1/2×4+1/3×5+1/4×6+1/5×7+……+1/8×10+1/9×11
以上数为列求和,每个数的分母都能写成n(n+2)即算式中每个数都可写作1/n(n+2) 其中n=2,3,4,5,6,7,8,9
因2/n(n+2)=（n+2-n)/（n(n+2)）=(1/n)-(1/（n+2 ）)
所以原式=（1/2-1/4+1/3-1/5+1/4-1/6+...+1/9-1/11)/2
=(1/2+1/3-1/10-1/11)/2
=53/165

=53/165

原式=1/2(1/2-1/4+1/3-1/5+1/4-1/6+1/5-1/7+...+1/8-1/10+1/9-1/11)
=1/2(1/2+1/3-1/10-1/11)
=53/165

1/2X(2+2)+1/3X(3+2)+1/4X(4+2)+……+1/8(8+2)+1/9(9+2)
=8+2(1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/9)
=8+2(1/2+1/3+1/6+1/4+1/8+1/5+1/7+1/9)
=8+2(1+3/8+1/5+1/7+1/9)
=10+2(3/8+1/5+1/7+1/9)到这就要自己算数啦
=10+2*(2089/2520)
=10+2089/1260
=14689/1260,

简算：1/1*2+1/2*3+1/3*4+1/4*5+1/5*6 巧算：(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4+1/5+1/6)-(1+1/2+1/3+1/4+1/5+1/6)*(1/2+1/3+1/4+1/5)===== [2^4+1/4)(4^4+1/4)(6^4+1/4)(8^4+1/4)(10^4+1/4)】/[1^4+1/4)(3^4+1/4)(5^4+1/4)(7^4+1/4)(9^4+1/4)] 1+1+1+1+1+1+1+1+1+2+5+4+8+3+6+2+1+4等于多少? 1/1*3+1/2*4+1/3*5+1/4*6+.+1/100*102=? 1+1+1+1+11+-1-1-1-1-2-3-4-5-6等于 1-1/2+1/3-1/4+1/5-1/6+1/7.-1/50=? 2×3/1+3×4/1+4×5/1+5×6/1+.199×200/1=? 1.（1+1/2+1/3+1/4）*（1/2+1/3+1/4+1/5）-（1+1/2+1/3+1/4+1/5）*（1/2+1/3+1/4）=2.（1+1/2+1/3+1/4+1/5）*（1/2+1/3+1/4+1/5+1/6）-（1+1/2+1/3+1/4+1/5+1/6）*（1/2+1/3+1/4+1/5）= 1/2{1/3[1/4(1/5x-1)-6]+4}=1 1/1*2*3+1/2*3*4+1/3*4*5+1/4*5*6---------+1/48*49*50 1*1/2+1/2*1/3+1/3*1/4+1/4*1/5+1/5*1/6+1/6*1/7用简便方法怎么做? 1/2*1/3+1/3*1/4+1/4*1/5+1/5*1/6 （简便方法） ((1/2)-1)*((1/3)-1)*((1/4)-1)*((1/5)-1)*((1/6)-1)*((1/7)-1)*((1/8)-1)*((1/9)-1)*((1/10)-1) 1-1/2+1/3-1/4+1/5-1/6+…+1/15=23*[1/( )+1/( )+1/( )+1/( )] 1+1/2+1/3+1/4+1/5+1/6+.+1/n极限多少? 1+1+1+2+1+3+1+4+1+5+1+6 1/2+1/3+1/4+1/5+1/6+1/7+.1/20=