(1/11+1/21+1/31++1/41)(1/21+1/31++1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)(1/21+1/31+1/41)=?

分类: 作业答案 • 2022-02-20 13:23:58

问题描述：

(1/11+1/21+1/31++1/41)*(1/21+1/31++1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)=?

答

设1/21+1/31+1/41＝Ａ,原式＝１／１１Ａ＋Ａ＾２＋１／５１Ａ＋１／１１＊１／５１－１／１１Ａ－１／５１Ａ－Ａ＾２＝１／１１＊１／５１＝１／５６１

(1/11+1/21+1/31++1/41)*(1/21+1/31++1/41+1/51)-(1/11+1/21+1/31+1/41+1/51)*(1/21+1/31+1/41)=?