- 244 名前：１３２人目の素数さん mailto:sage [2011/03/28(月) 09:52:08.74 ]
- >242
2行目から3行目に何を使ったのか分からない
1/(x+y) + 1/(y+z) + 1/(z+x) - 1/(x+y+z)
= 1/(x+y) + 1/(y+z) + 1/(z+x) - 3/(x+y+z) + 2/(x+y+z)
1/(x+y+z)で括る
= {1/(x+y+z)}*{(x+y+z)/(x+y) + (x+y+z)/(y+z) + (x+y+z)/(z+x) - 3} + 2/(x+y+z)
= {1/(x+y+z)}*{1 + z/(x+y) + 1 + x/(y+z) + 1 + y/(z+x) - 3} + 2/(x+y+z)
= {1/(x+y+z)}*{z/(x+y) + x/(y+z) + y/(z+x)} + 2/(x+y+z)
後は頼んだ>243
