1又1/2－5/6+7/12-9/20+11/30-13/42 关键是总结出公式,如d/n×(n+1)=.之类的

1又1/2－5/6+7/12-9/20+11/30-13/42 关键是总结出公式,如d/n×(n+1)=.之类的
1又1/2－5/6+7/12-9/20+11/30-13/42
关键是总结出公式,如d/n×(n+1)=.之类的

1又1/2－5/6+7/12-9/20+11/30-13/42 关键是总结出公式,如d/n×(n+1)=.之类的
1又1/2－5/6+7/12-9/20+11/30-13/42
=1+1/2-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7
如果本题有什么不明白可以追问,
另外发并点击我的头像向我求助,请谅解,

1又1/2－5/6+7/12-9/20+11/30-13/42
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7

1又1/2-5/6+7/12-9/20+11/30-13/42
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7

5/6=1/2+1/3
7/12=1/3+1/4
9/20=1/4+1/5
11/30=1/5+1/6
13/42=1/6+1/7
所以上面的式子为1+1/2--1/2--1/3+1/3+1/4--1/4--1/5+1/5+1/6--1/6--1/7=1--1/7=6/7
d/n(n+1)中d=n+(n+1)