Bài tập 1.23. Tính:
a) $\left(1+\frac{1}{2}-\frac{1}{4}\right)^{2}$ . $\left(2+\frac{3}{7}\right)$; b) 4 : $\left(\frac{1}{2}-\frac{1}{3}\right)^{3}$.
Bài Làm:
Trả lời:
a) $\left(1+\frac{1}{2}-\frac{1}{4}\right)^{2}$ . $\left(2+\frac{3}{7}\right)$ = $\left(\frac{4}{4}+\frac{2}{4}-\frac{1}{4}\right)^{2}$ . $\left(\frac{14}{7}+\frac{3}{7}\right)$ = $\left(\frac{5}{4}\right)^{2}$ . $\left(\frac{17}{7}\right)$ = $\frac{5^{2}}{4^{2}}$ . $\frac{17}{7}$ = $\frac{25.17}{16.7}$ = $\frac{425}{112}$
b) 4 : $\left(\frac{1}{2}-\frac{1}{3}\right)^{3}$ = 4 : $\left(\frac{3}{6}-\frac{2}{6}\right)^{3}$ = 4 : $\left(\frac{1}{6}\right)^{3}$ = 4 : $\frac{1^{3}}{6^{3}}$ = 4 . $6^{3}$ = 864