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Let x, y, and z be positive real numbers.  Find the largest possible value of

 

sqrt((3x + 4y)/(6x + 5y + 4z)) + sqrt((y + 2z)/(5x + 6y + 4z)) + sqrt((2z + 3x)/(x + 2y + 3z))

 Feb 8, 2024
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\(\sqrt{\frac{3x + 4y}{6x + 5y + 4z}} + \sqrt{\frac{y + 2z}{5x + 6y + 4z}} + \sqrt{\frac{2z + 3x}{x + 2y + 3z}}\)

So, largest value of that.

 

 

\(u=3x+4y,v=y+2z,w=3x+2z\)

we have

\(\sqrt{\frac{u}{u+v+w}}+\sqrt{\frac{v}{u+v+w}}+\sqrt{\frac{w}{u+v+w}}\)

and also

\(\sqrt{\frac{u}{u+v+w}}+\sqrt{\frac{v}{u+v+w}}+\sqrt{\frac{w}{u+v+w}}\le\sqrt{3}\)

You can google why. I can't write it in latex since idk how.

 

Answer: \({\sqrt{3}}\)

 Feb 10, 2024

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