Cách làm cho bạn:
a)$[(\frac{2}{5})^{6}.(\frac{2}{5})^{5}]:(\frac{2}{5})^{9}=[(\frac{2}{5})^{11}]/(\frac{2}{5})^{9}=(\frac{2}{5})^{2}=\frac{4}{25}$
b) $[(\frac{3}{7})^{8}:(\frac{3}{7})^{7}].(\frac{3}{7})=\frac{3}{7}.\frac{3}{7}=\frac{9}{49}$
c) $[(\frac{2}{5})^{9}.(\frac{2}{5})^{4}]:[(\frac{2}{5})^{7}.(\frac{2}{5})^{3}]=(\frac{2}{5})^{13}:(\frac{2}{5})^{10}=(\frac{2}{5})^{3}=\frac{8}{125}$
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