$\frac{1}{\frac{1}{a}+\frac{1}{b}}+\frac{1}{\frac{1}{c}+\frac{1}{d}} \leq \frac{1}{\frac{1}{a+b}+\frac{1}{c+d}}$
I think it has something to do with Harmonic mean, but can't fighre it out.
I think it has something to do with Harmonic mean, but can't fighre it out.