1/2+1/6+1/12+1/25+1/30+1/42+1/52

显示全部楼层 · 2012-6-29 13:22:33

1/2+1/6+1/12+1/25+1/30+1/42+1/52=1/2+1/（2*3）+1/（3*4）+1/25+1/（5*6）+1/（6*7）+1/52=1/2+1/2-1/3+1/3-1/4+1/25+1/5-1/6+1/52=1-1/4+1/25+1/5-1/6+1/52=3/4+6/25-1/6+1/52=7/12+6/25+1/52=9100/15600+3744/15600+300/15600=（9100+3744+300）/15600=13144/15600 楼上的都是错的...看清题没有？...

千问 · 2012-6-29 13:22:33

解：最后个数应该是1/56？1/2=1-1/21/6=1/2-1/31/12=1/3-1/41/20=1/4-1/51/30=1/5-1/61/42=1/6-1/71/56=1/7-1/8原式=1-1/2+1/2-1/3+1/3...+1/6-1/7+1/7-1/8=1-1/8=7/8...

千问 · 2012-6-29 13:22:33

是1/2+1/6+1/12+1/20+1/30+1/42+1/56=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=1-1/8=7/8...