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Решите задачу:

$1)4 {x}^{2} {y}^{5} \times 10 {x}^{2} {y}^{4} \times 2 {x}^{7} {y}^{2} = \\ 80 {x}^{11} {y}^{11}$

$2) {a}^{3} { b }^{5} \times 5 {a}^{6} {b}^{3} \times 4 {ab}^{2} = \\ 20 {a}^{10} {b}^{10}$

$3)( \frac{2}{5} + \frac{1}{2} ) \div ( - \frac{1}{5} ) + 4.5 =0 \\ 1) \frac{2}{5} + \frac{1}{2} = \frac{2 \times 2}{10} + \frac{5 \times 1}{2} =$

$= \frac{4}{10} + \frac{5}{10} = \frac{9}{10} \\ 2) \frac{9}{10} \div ( - \frac{1}{5} ) = - \frac{9}{10} \times \frac{5}{1} = - \frac{9}{2} =$

$= - 4.5 \\ 3) - 4.5 + 4.5 = 0$

$4)2 {a}^{2} {b}^{7} \times 25 {a}^{6} {b}^{3} \times 4 {a}^{2} = \\ 200 {a}^{10} {b}^{10}$

$5)( - \frac{4}{5} - \frac{7}{10} ) \div \frac{1}{2} + 3 = 0 \\ 1) - \frac{4}{5}-\frac{7}{10} = - \frac{8}{10}-\frac{7}{10} = - \frac{15}{10}$

$2) - \frac{ 15}{10} \div \frac{1}{2} = - \frac{15}{10} \times \frac{2}{1} = - \frac{15}{5} = \\ = - 3 \\ 3) - 3 + 3 = 0$

$6)5ab \times {a}^{2} \times 14 {a}^{2} {b}^{4} =70 {a}^{5} {b}^{5}$

$7)( \frac{1}{2} - \frac{7}{8} ) \div \frac{1}{4} + 2 = 0.5\\ 1) \frac{1}{2} - \frac{7}{8} = \frac{4}{8} - \frac{7}{8} = - \frac{3}{8}$

$2) - \frac{3}{8} \div \frac{1}{4} = - \frac{3}{8} \times \frac{4}{1} = \\ = - \frac{3}{2} = - 1.5$

$3) - 1.5 + 2 = 0.5$