Question

СРОЧНО СРОЧНО СРОЧНО​

Answer 1

1.

$\frac{12a}{ {a}^{2} - {b}^{2} } \times \frac{a - b}{4a} = \frac{12a \times (a - b)}{( {a}^{2} - {b}^{2} ) \times 4a } = \frac{4a \times 3 \times (a - b)}{(a - b)(a + b) \times 4a} = \frac{3}{a + b}$

2.

${( - \frac{ {a}^{5} }{2} )}^{3} = - \frac{ {( {a}^{5} )}^{3} }{ {2}^{3} } = - \frac{ {a}^{5 \times 3} }{8} = - \frac{ {a}^{15} }{8}$

3.

$16ab \times \frac{5 {b}^{2} }{32 {a}^{2} } = \frac{16ab \times 5 {b}^{2} }{32 {a}^{2} } = \frac{80a {b}^{3} }{32 {a}^{2} } = \frac{5 {b}^{3} }{2a}$

4.

$\frac{a + 7}{ {a}^{2} } \div \frac{3a + 21}{ {a}^{5} } = \frac{a + 7}{ {a}^{2} } \times \frac{ {a}^{5} }{3a + 21} = \frac{(a + 7) \times {a}^{5} }{ {a}^{2} \times (3a + 21)} = \frac{(a + 7) \times {a}^{2} \times {a}^{3} }{ {a}^{2} \times 3 \times (a + 7)} = \frac{ {a}^{3} }{3}$

5.

$\frac{ {b}^{2} + 7b }{10} \div (b + 7) = \frac{ {b}^{2} + 7b}{10} \div \frac{b + 7}{1} = \frac{ {b}^{2} + 7b}{10} \times \frac{1}{b + 7} = \frac{ {b}^{2} + 7b}{10 \times (b + 7)} = \frac{b \times (b + 7)}{10 \times (b + 7)} = \frac{b}{10}$