a) $$ \frac{2b}{1-b^2} + \frac{1}{1+b} = \frac{2b}{(1-b)(1+b)} + \frac{1}{1+b} = \frac{2b + 1-b}{(1-b)(1+b)} = \frac{b+1}{(1-b)(1+b)} = \frac{1}{1-b} $$
Ответ: $$ \frac{1}{1-b} $$