$f(x)=xg(x)$. Does the continuity of $f$ implies that $g$ is also continuous everywhere except zero?

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Let $f:\mathbb R^{m\times n}\to\mathbb R^m$ be a continuous function.

$x\in\mathbb R^{m\times n}$.

$g:\mathbb R^{m\times n}\to \mathbb R^n$.

$g(x)$ is a column vector, and $f(x)=xg(x)$.

Is it possible to conclude that $g$ is continuous everywhere except at zero?

It can also be easily shown that $g$ is continuous always imply the continuity of $f$.

Thank you for letting me know that $g(x)$ is not necessarily continuous at zero by counterexamples.


We assume that $x>0$ i.e. positive-semi-definite

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Let $f(x):\equiv0$, and $g(x):=0$ $(x\ne0)$, $\>g(0):=1$.

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No. There will always be a non-continuous $g$ with that property

Suppose that $f(x)=xg(x)$. If $g(x)$ is not continuous we're done. If $g(x)$ is continuous define $g'(x)=g(x)$ whenever $x\not = 0$ and $g'(0)=a$ for any $a$ such that $g(0)\not = a$. Then $g'$ is not continuous but $f(x)=xg'(x)$.

In other words you can always change the value of $g(x)$ at zero so you can't hope that $g$ will always be continuous.