Решебник по алгебре 7 класс Макарычев ФГОС Задание 140

 

\[\boxed{\text{140.}\text{\ }еуроки - ответы\ на\ пятёрку}\]

Пояснение.

Решение.

\[\textbf{а)}\ 0,3x = - 4\ \ \ \ | \cdot 10\]

\[3x = - 40.\]

\[\textbf{б)}\ 5x - 4 = 21\]

\[5x = 21 + 4\]

\[5x = 25.\]

\[\boxed{\text{140\ (}\text{с}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ 7,8 < 7,85 < 7,9\]

\[\textbf{б)}\ \frac{1}{3} > \frac{7}{24} > \frac{1}{4}\text{\ \ }\]

\[\ \frac{1}{3} = \frac{8}{24}\text{\ \ \ \ }и\ \ \frac{1}{4} = \frac{6}{24}\]

\[\textbf{в)} - 0,4 < - 0,32 < - 0,3\]

\[\textbf{г)}\frac{2}{3} < \frac{17}{24} < \frac{3}{4}\text{\ \ }\]

\[\ \frac{2}{3} = \frac{16}{24}\ \ и\ \ \ \frac{3}{4} = \frac{18}{24}\text{.\ }\]

\[\boxed{\text{140\ (}\text{н}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ |x - 2| - 6 = 17\]

\[|x - 2| = 17 + 6\]

\[|x - 2| = 23\]

\[x - 2 = 23\ \ \ \ \ \ \ \ \ \ \ \ \ x - 2 = - 23\]

\[x = 23 + 2\ \ \ \ \ \ \ \ \ \ \ \ x = - 23 + 2\]

\[x = 25\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - 21\]

\[Ответ:x = - 21;x = 25.\]

\[\textbf{б)}\ 31 + 4 \cdot |4 - x| = 47\ \]

\[4 \cdot |4 - x| = 47 - 31\]

\[4 \cdot |4 - x| = 16\]

\[|4 - x| = 16\ :4\]

\[|4 - x| = 4\]

\[4 - x = 4\ \ \ \ \ \ \ \ \ \ \ \ 4 - x = - 4\]

\[x = 4 - 4\ \ \ \ \ \ \ \ \ \ \ x = 4 - ( - 4)\]

\[x = 0\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 8\]

\[Ответ:x = 0;\ \ x = 8.\]