3) Выполним вычитание дробей:
$$\frac{2}{c+1} - \frac{c-1}{c^2+c} = \frac{2}{c+1} - \frac{c-1}{c(c+1)} = \frac{2c - (c-1)}{c(c+1)} = \frac{2c - c + 1}{c(c+1)} = \frac{c+1}{c(c+1)} = \frac{1}{c}.$$
Ответ: $$\frac{1}{c}$$