Tìm x, biết: 5/4 - 8x = 7/12

6/15

Tìm x, biết: \(\frac{5}{4} - 8x = \frac{7}{{12}}\)

\(x = \frac{{16}}{3}\);

\(x = \frac{1}{{12}}\);

\(x = \frac{{ - 16}}{3}\);

\(x = \frac{{ - 1}}{{12}}\).

Giải thích

Đáp án đúng là: B

\(\frac{5}{4} - 8x = \frac{7}{{12}}\)

\( - 8x = \frac{7}{{12}} - \frac{5}{4}\)

\( - 8x = \frac{7}{{12}} - \frac{{15}}{{12}}\)

\( - 8x = \frac{{ - 8}}{{12}}\)

\(x = \frac{{ - 8}}{{12}}:\left( { - 8} \right)\)

\(x = \frac{{ - 8}}{{12}} \cdot \frac{{ - 1}}{8}\)

\(x = \frac{1}{{12}}\). Vậy \(x = \frac{1}{{12}}\)