Упростите выражение: 1) 5b b+6 90 b-3 2b-6 b² +66;

1) $$\frac{5b}{b-3} - \frac{b+6}{2b-6} \cdot \frac{90}{b^2+6b} = \frac{5b}{b-3} - \frac{b+6}{2(b-3)} \cdot \frac{90}{b(b+6)} = \frac{5b}{b-3} - \frac{90}{2b(b-3)} = \frac{5b}{b-3} - \frac{45}{b(b-3)} = \frac{5b^2 - 45}{b(b-3)} = \frac{5(b^2 - 9)}{b(b-3)} = \frac{5(b-3)(b+3)}{b(b-3)} = \frac{5(b+3)}{b}$$

Ответ: $$\frac{5(b+3)}{b}$$