问题标题：
已知a2/3+b2/3=4,x=a+3a1/3b2/3,y=b+3a2/3b1/3,求（x+y）2/3+（x-y）2/3
问题描述：
已知a2/3+b2/3=4,x=a+3a1/3b2/3,y=b+3a2/3b1/3,求（x+y）2/3+（x-y）2/3
牛丽娜回答：
x+y=a+b+3a^(1/3)b^(2/3)+3a^(2/3)b^(1/3)=[a^(1/3)]^3+3[a^(1/3)]^2b^(1/3)+3a^(1/3)[b^(1/3)]^2+[b^(1/3)]^3=[a^(1/3)+b^(1/3)]^3x-y=a-b+3a^(1/3)b^(2/3)-3a^(2/3)b^(1/3)=[a^(1/3)]^3-3[a^(1/3)]^2b^(1/3)+3a^(1...
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