简算3/2*5+3/5*8+3/8*11+3/11*14+3/14*17+3/17*20
答案:2 悬赏:70
解决时间 2021-11-05 08:43
- 提问者网友:容嬷嬷拿针来
- 2021-11-04 12:36
简算3/2*5+3/5*8+3/8*11+3/11*14+3/14*17+3/17*20
最佳答案
- 二级知识专家网友:独钓一江月
- 2021-11-04 13:21
裂项法:
3/2*5+3/5*8+3/8*11+3/11*14+3/14*17+3/17*20
=1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20
=1/2-1/20
=9/20
3/2*5+3/5*8+3/8*11+3/11*14+3/14*17+3/17*20
=1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20
=1/2-1/20
=9/20
全部回答
- 1楼网友:逐風
- 2021-11-04 14:09
有括号吗?没有括号是很麻烦的。如果有括号的话:
3/(2*5)+3/(5*8)+3/(8*11)+3/(11*14)+3/(14*17)+3/(17*20)
=(1/2-1/5)+(1/5-1/8)+(1/8-1/11)+(1/11-1/14)+(1/14-1/17)+(1/17-1/20)
=1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20
=1/2-1/20
=10/20-1/20
=9/20
3/(2*5)+3/(5*8)+3/(8*11)+3/(11*14)+3/(14*17)+3/(17*20)
=(1/2-1/5)+(1/5-1/8)+(1/8-1/11)+(1/11-1/14)+(1/14-1/17)+(1/17-1/20)
=1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20
=1/2-1/20
=10/20-1/20
=9/20
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