Question 85
If $a$ and $b$ are two positive numbers not greater than $1$ prove that
$$
\frac{a+b}{1+a b} \leq \frac{1}{1+a}+\frac{1}{1+b}
$$
When does the equality hold?
$$
\frac{a+b}{1+a b} \leq \frac{1}{1+a}+\frac{1}{1+b}
$$
When does the equality hold?