Câu 1.23 :
a. $\left ( 1+\frac{1}{2}-\frac{1}{4} \right )^{2}. \left ( 2+\frac{3}{7} \right )$ = $\left ( \frac{4}{4}+\frac{2}{4}-\frac{1}{4} \right )^{2}. \left ( \frac{14}{7}+\frac{3}{7} \right )$= $\left ( \frac{5}{4} \right )^{2}$. $\frac{17}{7}$= $\frac{25}{16}$. $\frac{17}{7}$ = $\frac{425}{112}$
b. 4: $\left ( \frac{1}{2}-\frac{1}{3} \right )^{3}$= 4: $(\frac{3-2}{2.3})^{3}$ = 4: $\frac{1}{6^{3}}$ = 4. $6^{3}$= 864