Cho hai biểu thức [B = , , left( { frac{2}{3} - 1 frac{1}{2}} right): frac{4}{3} + frac{1}{2} ] và [C = , frac{9}{{23}}. frac{5}{8} + frac{9}{{23}}. frac{3}{8} - frac{9}{{23}} ] ....

* Hướng dẫn giải

\[B = \,\,\left( {\frac{2}{3} - 1\frac{1}{2}} \right):\frac{4}{3} + \frac{1}{2}\]

\[ = \left( {\frac{2}{3} - \frac{3}{2}} \right).\frac{3}{4} + \frac{1}{2}\]

\[ = \frac{{ - 5}}{6}.\frac{3}{4} + \frac{1}{2}\]

\[ = \frac{{ - 5}}{8} + \frac{1}{2}\]

\[ = \frac{{ - 1}}{8}.\]

\[\begin{array}{*{20}{l}}{C = \,\frac{9}{{23}}.\frac{5}{8} + \frac{9}{{23}}.\frac{3}{8} - \frac{9}{{23}}}\\{ = \frac{9}{{23}}.\left( {\frac{5}{8} + \frac{3}{8} - 1} \right)}\\{ = \frac{9}{{23}}.\left( {1 - 1} \right)}\\{ = \frac{9}{{23}}.0}\\{ = 0.}\end{array}\]

Vậy C = 0; B

Đáp án cần chọn là: A