To prove the inequality, we homogenize both ends, which is equivalent to proving:
a3(bc)1+b3(c+a)1+c3(a+b)1⩾2(abc)343
Let a=x3,b=y3,c=z3, substituting into the above inequality, we get:
cyc∑x9(y3+z3)1⩾2x4y4z43
By Muirhead's inequality, we have:
That is,
(∑symx12y12−∑symx11y8z5)+2(∑symx12y9z3−∑symx11y8z5)+(∑symx9y9z6−∑symx8y8z8)⩾0
sym∑x12y12+2sym∑x12y9z3+sym∑x9y9z6⩾3sym∑x11y8z5+6x8y8z8
Therefore, inequality (1) holds, and thus the original inequality holds.