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Question Number 4679 by 314159 last updated on 22/Feb/16

L e t a, b, c, d \in R, a + b + c + d = 0 . P r o v e t h a t

\sum_{c y c} (\frac{1}{\sqrt{a^{2} + a + 1}}) ⩽ 4 .

Commented by prakash jain last updated on 21/Feb/16

It is not much less than 4 .

a = b = c = d = 0

Σ \frac{1}{\sqrt{a^{2} + a + 1}} = 4

Do you mean ⩽ 4 ? (less than or equal to) ?

Commented by 314159 last updated on 22/Feb/16

Yeah . S o r r y \dots

It is ⩽ (less than or equal to) .

Thanks . .

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