【就一部不懂】如果x、y∈R,且x≠y,比较(x2+y2)2与xy(x+y)2大小
作差法
(x2+y2)2-xy(x+y)2
=x＾4+y＾4+2x＾2y＾2-x＾3y-2x＾2y＾2－xy＾3
=(x-y)(x＾3-y＾3)
=(x-y)＾2[(x+y/2)＾2+3y＾2/4]
∵x≠y
(x-y)＾2＞0,(x+y/2)＾2+3y＾2/4>0
∴(x2+y2)2＞xy(x+y)2
=(x-y)＾2[(x+y/2)＾2+3y＾2/4] 这部是怎么做出来的?