Bài 6 trang 21 toán 7 tập 1 CTST
Tính:
a) $\left [ \left ( \frac{3}{7} \right )^{4} . \left ( \frac{3}{7} \right )^{5} \right ] : \left ( \frac{3}{7}\right)^{7}$
b) $\left [ \left ( \frac{7}{8} \right )^{5} : \left ( \frac{7}{8} \right )^{4} \right ] . \frac{7}{8}$
c) [(0,6}3 . (0,6}8)] : [ (0,6)7 . (0,6)2 ]
Bài Làm:
a) $\left [ \left ( \frac{3}{7} \right )^{4} . \left ( \frac{3}{7} \right )^{5} \right ] : \left ( \frac{3}{7}\right)^{7}$ = $\left ( \frac{3}{7}\right)^{9}$ : $\left ( \frac{3}{7}\right)^{7}$ = $\left ( \frac{3}{7}\right)^{2}$ = $\frac{9}{49}$
b) $\left [ \left ( \frac{7}{8} \right )^{5} : \left ( \frac{7}{8} \right )^{4} \right ] . \frac{7}{8}$ = $\frac{7}{8} . \frac{7}{8}$ = $\left ( \frac{7}{8}\right)^{2}$ = $\frac{49}{64}$
c) [(0,6)3 . (0,6)8] : [ (0,6)7 . (0,6)2 ] = (0,6)11 : (0,6)9 = (0,6)2 = 0,36