首页 > 留学知识库

问题: 数学

(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)—(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)

解答:

不知道你想怎么算,最直接的算法就是通分后直接做,也不复杂,要是追求简便方法的话就用整体思想吧
原式=(1+1/2+1/3+1/4)×[(1/2+1/3+1/4)+1/5]-[(1+1/2+1/3+1/4)+1/5]×(1/2+1/3+1/4)
=(1+1/2+1/3+1/4)×(1/2+1/3+1/4)+(1+1/2+1/3+1/4)×(1/5)-
(1+1/2+1/3+1/4)×(1/2+1/3+1/4)-(1/5)*(1/2+1/3+1/4)
=(1/5)*[(1+1/2+1/3+1/4)-(1/2+1/3+1/4)]
=1/5