Упр.12 Повторение ГДЗ Мордкович Семенов 7 класс (Алгебра)

а) ((5/12 — 2/3) · 0,2^2) / (5,7 — 5 3/4); б) (-2 1/40 + 1,125) / (0,3^2 · (8/15 — 4/5)).

а)

$$ \frac{\left(\frac{5}{12}-\frac{2}{3}\right)\cdot 0{,}2^2}{5{,}7-5\frac{3}{4}} = \frac{\left(\frac{5}{12}-\frac{8}{12}\right)\cdot 0{,}04}{5{,}7-5{,}75} = \frac{-\frac{3}{12}\cdot 0{,}04}{-0{,}05} $$

$$ \frac{-\frac{1}{4}\cdot 0{,}04}{-0{,}05} = \frac{-0{,}01}{-0{,}05} = 0{,}2 $$

б)

$$ \frac{-2\frac{1}{40}+1{,}125}{0{,}3^2\cdot\left(\frac{8}{15}-\frac{4}{5}\right)} = \frac{-\frac{81}{40}+\frac{9}{8}}{0{,}09\cdot\left(\frac{8}{15}-\frac{12}{15}\right)} = \frac{-\frac{81}{40}+\frac{45}{40}}{0{,}09\cdot\left(-\frac{4}{15}\right)} $$

$$ = \frac{-\frac{36}{40}}{-\frac{0{,}36}{15}} = \frac{36}{40}\cdot\frac{15}{0{,}36} = \frac{9}{10}\cdot\frac{1500}{36} = 37{,}5 $$

Ответ

а) $$0{,}2$$; б) $$37{,}5$$.