√a + √(a-1) > √(a-2) + √(a-3)
1 / {√a+√(a-1)} < 1 / {√(a-2)+√(a-3)}
{√a-√(a-1)} / [ {√a+√(a-1)}{√a-√(a-1)} ] < {√(a-2)-√(a-3)} / [ {√(a-2)+√(a-3)}{√(a-2)-√(a-3)} ]
{√a-√(a-1)} / { a - (a-1)} < {√(a-2)-√(a-3)} / { (a-2) - (a-3)}
{√a-√(a-1)} < {√(a-2)-√(a-3)}
证明完毕