AT-OEMO-BEG 2020 Problem 1

Let $a$ be a real number and $b$ a real number with $b\neq-1$ and $b\neq0.$ Find all pairs $(a, b)$ such that $$\frac{(1 + a)^2 }{1 + b}\leq 1 + \frac{a^2}{b}.$$ For which pairs (a, b) does equality apply? (Walther Janous)