1) Упростите выражение: $$\frac{3a}{a-3} + \frac{a+5}{6-2a} \cdot \frac{54}{5a+a^2}$$;

$$\frac{3a}{a-3} + \frac{a+5}{6-2a} \cdot \frac{54}{5a+a^2} = \frac{3a}{a-3} + \frac{a+5}{2(3-a)} \cdot \frac{54}{a(5+a)} = \frac{3a}{a-3} - \frac{a+5}{2(a-3)} \cdot \frac{54}{a(a+5)} = \frac{3a}{a-3} - \frac{54}{2a(a-3)} = \frac{3a}{a-3} - \frac{27}{a(a-3)} = \frac{3a^2 - 27}{a(a-3)} = \frac{3(a^2 - 9)}{a(a-3)} = \frac{3(a-3)(a+3)}{a(a-3)} = \frac{3(a+3)}{a}$$