А2. Упростите выражение: 15b 6b 7b+35 5-b+b²-25-3.

$$ \frac{15b}{5-b} + \frac{6b}{b^2-25} - \frac{7b+35}{3} = \frac{15b}{5-b} + \frac{6b}{(b-5)(b+5)} - \frac{7(b+5)}{3} = \frac{-15b}{b-5} + \frac{6b}{(b-5)(b+5)} - \frac{7(b+5)}{3} = \frac{-15b \cdot 3(b+5) + 6b \cdot 3 - 7(b+5)(b-5) }{3(b-5)(b+5)} = \frac{-45b^2-225b + 18b - 7b^2+175}{3(b-5)(b+5)} = \frac{-52b^2 - 207b + 175}{3(b-5)(b+5)} $$

Ответ:$$ \frac{-52b^2 - 207b + 175}{3(b-5)(b+5)} $$