(1\5+1\7+9\1+1\11)x(1\7+1\9+1\11+1\13)-(1\5+1\7+1\9+1\11+1\13)x(1\7+1\9+1\11)

分类: 作业答案 • 2022-05-26 12:38:29

问题描述：

答

令a=1\5+1\7+9\1+1\11
b=1\7+1\9+1\11+1\13
则原式=ab-(a+1/13)(b-1/13)
=ab-ab+a/13-b/13+1/169
=(a-b)/13+1/169
=(1/5-1/13)/13+1/169
=1/65-1/169+1/169
=1/65