Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}a)\left| x \right| - {\rm{ }}2,5{\rm{ }} = {\rm{ }}27,5\\ \Leftrightarrow \left| x \right| = 27,5 + 2,5\\ \Leftrightarrow \left| x \right| = 30\\ \Leftrightarrow x = 30\,\,\,\,hoac\,\,\,x = - 30\end{array}\)
\(\begin{array}{l}b){\rm{ }}3/4 + 2/5.x{\rm{ }} = 29/36\\ \Leftrightarrow \frac{3}{4} + \frac{2}{5}x = \frac{{29}}{{36}}\\ \Leftrightarrow \frac{2}{5}x = \frac{{29}}{{36}} - \frac{3}{4}\\ \Leftrightarrow \frac{2}{5}x = \frac{1}{{18}}\\ \Leftrightarrow \,\,\,\,\,\,x = \frac{1}{{18}}:\frac{2}{5}\\ \Leftrightarrow \,\,\,\,\,\,x = \frac{5}{{36}}\end{array}\)
