TITLE: How prove this function inequality $xf(x)>\frac{1}{x}f\left(\frac{1}{x}\right)$
QUESTION [11 upvotes]: Let $f(x)$ be monotone decreasing on $(0,+\infty)$, such that
  $$0<f(x)<\lvert f'(x) \rvert,\qquad\forall x\in (0,+\infty).$$
Show that
  $$xf(x)>\dfrac{1}{x}f\left(\dfrac{1}{x}\right),\qquad\forall x\in(0,1).$$

My ideas:
Since
$f(x)$ is monotone decreasing, $f'(x)<0$, hence
$$f(x)+f'(x)<0.$$
Let
$$F(x)=e^xf(x)\Longrightarrow F'(x)=e^x(f(x)+f'(x))<0$$
so
$F(x)$ is also monotone decreasing. Since $0<x<1$,
$$F(x)>F\left(\dfrac{1}{x}\right)$$
so
$$e^xf(x)>e^{\frac{1}{x}}f\left(\frac1x\right).$$
So we must prove
$$e^{\frac{1}{x}-x}>\dfrac{1}{x^2},\qquad0<x<1$$
$$\Longleftrightarrow \ln{x}-x>\ln{\dfrac{1}{x}}-\dfrac{1}{x},0<x<1$$
because $0<x<1,\dfrac{1}{x}>1$ so I can't. 
But I don't know whether this inequality is true. I tried Wolfram Alpha but it didn't tell me anything definitive.
PS: This problem is from a Chinese analysis problem book by Huimin Xie.

REPLY [4 votes]: I think the answer by @Kelenner is really good. This answer is just to prove the inequality 
$$
e^{1/x-x}>1/x^2,\quad 0<x<1.\tag{*}
$$
that was discussed in the post/comments. We apply the logarithm, and since the logarithm is monotonically increasing, the inequality $(*)$ is equivalent to
$$
2\ln x>x-\frac{1}{x},\quad 0<x<1.\tag{**}
$$
Let
$$
g(x)=2\ln x-x+\frac{1}{x}.
$$
Then $g(1)=0$ and a differentiation (and simplification) gives
$$
g'(x)=-\frac{(x-1)^2}{x^2}.
$$
Hence $g'(x)<0$ for $0<x<1$ (so $g$ is monotonically decreasing) and it follows that $g(x)>0$ for $0<x<1$ and thus that $(**)$ holds. But $(**)$ was seen to be equivalent to $(*)$, and so the inequality $(*)$ is true.
Edit: I updated the solution without the change of variable, since I don't think it simplified anything in the end.