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

$$\frac{15b}{5-b} + \frac{6b}{b^2-25} : \frac{7b+35}{3}$$ = $$\frac{15b}{5-b} + \frac{6b}{(b-5)(b+5)} : \frac{7(b+5)}{3}$$ = $$\frac{15b}{5-b} + \frac{6b}{(b-5)(b+5)} \cdot \frac{3}{7(b+5)}$$ = $$\frac{15b}{5-b} + \frac{18b}{7(b-5)(b+5)^{2}}$$ = $$\frac{-15b(b-5)}{b^2-25} + \frac{18b}{7(b-5)(b+5)^{2}}$$ = $$\frac{-105b(b+5)^{2}+18b}{7(b-5)(b+5)^{2}}$$ = $$\frac{b(-105(b+5)^{2}+18)}{7(b-5)(b+5)^{2}}$$ = $$\frac{b(-105b^{2}-1050b-2625+18)}{7(b-5)(b+5)^{2}}$$ = $$\frac{b(-105b^{2}-1050b-2607)}{7(b-5)(b+5)^{2}}$$.

Ответ: $$\frac{b(-105b^{2}-1050b-2607)}{7(b-5)(b+5)^{2}}$$.