Let $a,b,c$ be the lengths of the sides of a triangle. Prove that
$\sqrt{a+b−c}+\sqrt{b+c−a}+\sqrt{c+a−b} \leq \sqrt{a}+\sqrt{b}+\sqrt{c}$.
(1996)
APMO ! How Nice
- Nadim Ul Abrar
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Re: APMO ! How Nice
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Nur Muhammad Shafiullah | Mahi
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Re: APMO ! How Nice
Well,just my solution used the same thing Mahi vai suggested.*Mahi* wrote:Ravi's transformation, and then QM-AM inequality.
As $a,b,c$ are the sides of a triangle, we can assume that $a=y+z,b=z+x,c=x+y$. Thus $a+b-c=2z,b+c-a=2x,c+a-b=2y$. Now the inequality becomes $\sqrt {2x}+\sqrt {2y}+\sqrt {2z}\leq \sqrt {x+y}+\sqrt {y+z}+\sqrt {z+x}$.
This time apply the QM-HM inequality,
$\sqrt {2x}+\sqrt {2y}+\sqrt {2z}=\frac{\sqrt {2x}+\sqrt {2y}}{2}+\frac{\sqrt {2y}+\sqrt {2z}}{2}+\frac{\sqrt {2z}+\sqrt {2x}}\leq \sqrt {\frac{2x+2y}{2}}+\sqrt {\frac{2y+2z}{2}}+\sqrt {\frac{2z+2x}{2}}=\sqrt {x+y}+\sqrt {y+z}+\sqrt {z+x}$.
$\color{blue}{\textit{To}} \color{red}{\textit{ problems }} \color{blue}{\textit{I am encountering with-}} \color{green}{\textit{AVADA KEDAVRA!}}$
- Phlembac Adib Hasan
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Re: APMO ! How Nice
কী? এইটা এপিএমও? হায়রে আবার আমার নিজের বানানো অঙ্ক বেদখল দিসে।Nadim Ul Abrar wrote:Let $a,b,c$ be the lengths of the sides of a triangle. Prove that
$\sqrt{a+b−c}+\sqrt{b+c−a}+\sqrt{c+a−b} \leq \sqrt{a}+\sqrt{b}+\sqrt{c}$.
(1996)
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Re: APMO ! How Nice
Actually it is QM-AM, not QM-HM (there isn't any use of harmonic mean here).SANZEED wrote: This time apply the QM-HM inequality,
$\cdots \frac{\sqrt {2x}+\sqrt {2y}}{2}+\frac{\sqrt {2y}+\sqrt {2z}}{2}+\frac{\sqrt {2z}+\sqrt {2x}}2 \leq \sqrt {\frac{2x+2y}{2}}+\sqrt {\frac{2y+2z}{2}}+\sqrt {\frac{2z+2x}{2}} \cdots$
আহারে, এইটা তোর জন্মের আগের না পরের?Phlembac Adib Hasan wrote: কী? এইটা এপিএমও? হায়রে আবার আমার নিজের বানানো অঙ্ক বেদখল দিসে।
Please read Forum Guide and Rules before you post.
Use $L^AT_EX$, It makes our work a lot easier!
Nur Muhammad Shafiullah | Mahi
Use $L^AT_EX$, It makes our work a lot easier!
Nur Muhammad Shafiullah | Mahi
- Phlembac Adib Hasan
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Re: APMO ! How Nice
আগের।*Mahi* wrote:আহারে, এইটা তোর জন্মের আগের না পরের?Phlembac Adib Hasan wrote: কী? এইটা এপিএমও? হায়রে আবার আমার নিজের বানানো অঙ্ক বেদখল দিসে।
ধুর, আর বিশটা বছর আগে ক্যান যে জন্ম হইল না
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