设 x =√(5/12) +√(1/5),
y =√(1/3) +√(2/7).
则 x^2 =5/12 +1/5 +2√(1/12)
=37/60 +√(1/3),
y^2 =1/3 +2/7 +2√(2/21)
=13/21 +√(8/21).
因为 1/3