90个埃及数:1/2,1/3,1/4,1/5,…,1/90,1/91,挑10个,加正负号,使它们的和为-1
问题描述:
90个埃及数:1/2,1/3,1/4,1/5,…,1/90,1/91,挑10个,加正负号,使它们的和为-1
答
-1=-1/5-1/6-1/8-1/9-1/10-1/12-1/15-1/18-1/20-1/24
90个埃及数:1/2,1/3,1/4,1/5,…,1/90,1/91,挑10个,加正负号,使它们的和为-1
-1=-1/5-1/6-1/8-1/9-1/10-1/12-1/15-1/18-1/20-1/24