If X and Y are positive, which of the following must be greater than 1 / √(x+y)?
1. √(X+Y)/ 2x
2. √X + √Y / (x+y)
3. √X - √Y / (x+y)

1. We can simplify as IS √(x+y)/2x > √(x+y)/x+y ? i.e. 1/2x '>' 1/x+y ? ...Not True.
2. We can simplify as IS √X + √Y / (x+y) '>' √(x+y)/x+y ?
i.e. √X + √Y > √(x+y) ? Always True.
3. We can simplify as IS √X - √Y / (x+y) '>' √(x+y)/x+y ?
i.e. √X - √Y > √(x+y) ? ....Not True.