已知a^(2/3)+b^(2/3)=4，x=a+3a^(1/3)b^(2/3),y=b+3a^(2/3)b^91/3)

令 m = a^(1/3), n = b^(1/3)
则 a = m^3, b = n^3
由条件第一式可知 m^2 + n^2 = 4
而 x = m^3 + 3mn^2, y = n^3 + 3m^2n
所以
(x+y)^(2/3) = (m^3 + 3m^2n + 3mn^2 + n^3)^(2/3) = (m+n)^2
同理 (x-y)^(2/3) = (m-n)^2

所以 (x+y)^(2/3)+(x-y)^(2/3) = (m+n)^2 + (m-n)^2
= 2(m^2 + n^2) = 2 * 4 = 8

晕了~~数学题？？？求什么呢？？？x,y？？？