化简1·1!+2·2!+3·3!+…+n·n!=___________
来源:百度知道 编辑:UC知道 时间:2024/05/31 10:40:55
n*n!=(n+1-1)*n!
=(n+1)!-n!
所以原式=2!-1!+3!-2!。。。。。+(n+1)!-n!
=(n+1)!-1
讨论一般项:因为
k*k!=(k+1-1)*k!
=(k+1)!-k!
所以原式=2!-1!+3!-2!。。。。。+(n+1)!-n!
=(n+1)!-1
1·1!+2·2!+3·3!+…+n·n
=1方+2方+3方+....+n方
=n+n三次方/2
其实好像跟1+2+3+....+n差不多~(首项+末项)*项数÷2
我是觉得这样,不一定对~
原式=2*1!+3*2!+…+(n+1)*n!-(1!+2!+…n!)
=2!+3!+…+(n+1)!-(1!+2!+…n!)
=(n+1)!-1
化简1·1!+2·2!+3·3!+…+n·n!=___________
1×2×3×······×9999=?
1+1/(1+2)+1/(1+2+3)+···1/(1+2+3+···+100)等于几?
(1-1/2-1/3-······-1/2006 )*(1/2+1/3+1/4·····
1×1+2×2+3×3+4×4···100×100=
(1+1/2+1/3+·····+1/n)/n
1:成语填空·2。。。3。。。
1,-2,3,-4,-5,6,-7,-8,-9,10,-11,······
小学数学题:10/(1*2)+20/(1*2*3)+30/(1*2*3*4)+·····+90/(1*2*3*···*10)=
小学数学题3-2/(1*2)-7/(1*2*3)-14/(1*2*3*4)-····-98/(1*2*3*···*10)=?