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VN TST 2021 Question 4

VMO · VN TST 2021

Question 4

Let $a,b,c$ be nonnegative real numbers such that
$$2(a^2+b^2+c^2)+3(ab+bc+ca)=5(a+b+c).$$
Prove that
$$4(a^2+b^2+c^2)+2(ab+bc+ca)+7abc\le25.$$