All these roots

Algebra Level 5

x y + z + y x + z + z x + y + 2 2 ( x 2 + y 2 + z 2 ) x y + y z + x z \large \sqrt{\frac{x}{y+z}}+\sqrt{\frac{y}{x+z}}+\sqrt{\dfrac{z}{x+y}}+2\sqrt{\dfrac{2(x^2+y^2+z^2)}{xy+yz+xz}}

Let x , y x,y and z z be positive reals . If the minimum value of the expression above can be expressed in the form α β γ \dfrac{\alpha\sqrt{\beta}}{\gamma} , where α , β \alpha,\beta and γ \gamma are positive integers with β \beta square-free and α \alpha and γ \gamma coprime, find α + β + γ \alpha +\beta +\gamma .


The answer is 11.

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1 solution

Dragan Marković
May 21, 2016

x y + z = < x 2 y z \sqrt{\frac{x}{y+z}}=<\sqrt{\frac{x}{2\sqrt{yz}}} and so on in the end we get that the minima is 3 2 + 2 2 \frac{3}{\sqrt{2}} +2\sqrt{2} and with a little arrangement we get 7 2 2 \frac{7\sqrt{2}}{2} that gives us the answer 11.

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