1992 IMO Problems/Problem 2: Difference between revisions

Revision as of 09:24, 20 November 2023

Problem

Let $\mathbb{R}$ denote the set of all real numbers. Find all functions $f:\mathbb{R} \to \mathbb{R}$ such that

$f\left( x^{2}+f(y) \right)= y+(f(x))^{2} \hspace{0.5cm} \forall x,y \in \mathbb{R}$

Solution

We notice that the right hand side of the equation has $y$ , therefore the only way that $f\left( x^{2}+f(y) \right)$ produces that $y$ is if $f(y)=y$ .

This makes the equation as $f\left( x^{2}+y \right)= y+(f(x))^{2}$

Since $f(y)=y$ , then $f(x)=x$ , thus $f\left( x^{2}+y \right)=x^{2}+y=y+(f(x))^{2}=y+x^{2}$ and the equation holds true.

Only solution to this problem is $f(x)=x$

~Tomas Diaz. orders@tomasdiaz.com

Alternate solutions are always welcome. If you have a different, elegant solution to this problem, please add it to this page.

@@ Line 14: / Line 14: @@
 Only solution to this problem is <math>f(x)=x</math>
+~Tomas Diaz. orders@tomasdiaz.com
 {{alternate solutions}}

1992 IMO (Problems) • Resources
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1992 IMO Problems/Problem 2: Difference between revisions

Revision as of 09:24, 20 November 2023

Problem

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