1. $\frac{2a^{2}}{a+1} \div \frac{a^{2}-a}{a^{2}-1} =$

2. $\frac{5x^{2}-25x}{x^{2}-7x+10} \times \frac{x^{2}-4}{15x^{2}} =$

3. $\frac{x+4}{3x^{2}-12x} \div \frac{x^{2}+8x+16}{x^{2}-4x}$

4. ب: $\frac{6x^{2}-6}{x-6} \div \frac{x^{2}+7x+6}{x^{2}-36} =$

5. $\frac{10x}{x^{2}} \times \frac{x^{2}-2x}{5x^{2}}$