Question

срочно !!!! 21 бал !!!!!​

Answer 1

Объяснение:

$1) \frac{ {a}^{2} - 81 }{2 {a}^{2} + 18a } = \frac{(a - 9)(a + 9)}{2a(a + 9)} = \frac{a - 9}{2a} \\ \\ \frac{4.5 - 9}{2 \times 4.5} = - \frac{4.5}{9} = - \frac{1}{2} = - 0.5$

$\frac{ {a}^{2} - 25 {b}^{2} }{5ab} \div ( \frac{1}{5b} - \frac{1}{a} ) = \frac{ (a - 5b)(a + 5b)}{5ab} \div \frac{a - 5b}{5ab} = \frac{(a - 5b)(a + 5b) \times 5ab}{5ab \times (a - 5b)} = a + 5b \\ \\ 8 \frac{1}{16} + 5 \times 6 \frac{3}{16} = 8 \frac{1}{16} + \frac{495}{16} = 8 \frac{1}{16} + 30 \frac{15}{16} = 39$