<s>[INST] Symmetric Olympiad inequality Prove that for all positive reals $a, b, c$ this inequality holds:
$$\sum_{cyc}\frac{a^3}{b^2 - bc + c^2} \ge \sum_{cyc}a$$
I have proved this in a very ugly way:
I multiplied with $(a^2 - ab + b^2)(b^2 - bc + c^2)(c^2 - ca + a^2)$ and with some work i managed to prove this with Schur. I find this way boring and time-consuming. My question is - Is there a nicer solution to this?
Source: Mildorf Inequalities
 [/INST] Note by CS (with $\sum$ denoting cyclic sums):
$$ \sum \frac{a^3}{b^2-bc+c^2} \geqslant \frac{\left(\sum a^2 \right)^2}{\sum a(b^2-bc+c^2)}$$
Hence it is enough to show
$$\left(\sum a^2 \right)^2 \geqslant \left(\sum a\right) \cdot \sum a(b^2-bc+c^2)$$
$$\iff \sum a^4 + 2\sum a^2b^2 \geqslant \sum (2a^2b^2-a^2bc + b^3a+ ac^3)$$
which is just the fourth degree Schur inequality:
$$\sum a^4 + abc\sum a \geqslant \sum ab(a^2+b^2) $$
Equality is when $a=b=c$, or when any one variable is $0$ and the other two equal.
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