作业帮1/3+1/(3+4)+1/(3+4+5)+...+1/(3+4+5+...+20)如何解?
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1/3+1/(3+4)+1/(3+4+5)+...+1/(3+4+5+...+20)如何解?
1/3+1/(3+4)+1/(3+4+5)+...+1/(3+4+5+...+20)如何解?
1/3+1/(3+4)+1/(3+4+5)+...+1/(3+4+5+...+20)如何解?
1/(3+4+……+n)=2/((n+3)*(n-2))=0.4*(1/(n-2)-1/(n+3))
1/3=0.4*(1-1/6)
1/(3+4)=0.4*(1/2-1/5)
类推
1/(3+4+……+20)=0.4*(1/18-1/23)
所以原式
=0.4*((1+1/2+1/3+……+1/18)-(1/6+1/7+……+1/23))
=0.4*(1+1/2+1/3+1/4+1/5-1/19-1/20-1/21-1/22-1/23)
1/3+1/(3+4)+1/(3+4+5)+...+1/(3+4+5+...+20)如何解?
(1+1/2+1/3+1/4+1/5)*(1/3+1/4+1)-(1+1/3+1/4)*(1/2+1/3+1/4+1/5)
3/1：4/1：5/1化简是?
1/3:1/4:1/5化简
1+1 2+2 3+3 4+4 5+5
(1/3+1/4+1/5+...+1/1999)+(2/3+3/4+4/5+...+1998/19999)
/1/3-1/2/+/1/4-1/3/+/1/5-1/4/+.+/1/10-1/9/
|1/3-1/2|+|1/4-1/3|+|1/5-1/4|+.+|1/2008-1/2007|
|1/3-1/2|+|1/4-1/3|+|1/5-1/4|+...+|1/10-1/9|
1,2,3,4,5
1,2,3,4,5,
1 2 3 4 5
1,2,3,4,5
化简1/3:4/5
1,2,3,4,5,
1 2 3 4 5
1,2,3,4,5,
.1,2,3,4,5,