教我一题

11 |

1/12+1/20+1/30+1/36+1/42=1/3*4+1/4*5+1/5*6+1/6*7=(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)=1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7=1/3-1/7=4/21

千问 | 2007-5-18 17:09:05 | 显示全部楼层

1/12+1/20+1/30+1/36+1/42=1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/36=1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/36=1/3-1/7+1/36=(84-36+7)/252=55/252

千问 | 2007-5-18 17:09:05 | 显示全部楼层

原式=1/3*4+1/4*5+1/5*6+1/6*7+1/36
=1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/36
=1/3-1/7+1/36

千问 | 2007-5-18 17:09:05 | 显示全部楼层

通分把分母都化成最小公倍数!再进行加减,分子相加分母不不变,要注意啊!!!!!!!!!

主题	0 回帖	4882万积分

Rank: 8 Rank: 8

热门排行