Tính a) [(3/7)^4 . (3/7)^5] : (3/7)^ 7; b) [(7/8)^5 : (7/8)^4] . 7/8

* Hướng dẫn giải

$$\begin{gathered} a) \left[{\left(\frac{3}{7}\right)}^4.{\left(\frac{3}{7}\right)}^5\right]:{\left(\frac{3}{7}\right)}^7=\left[{\left(\frac{3}{7}\right)}^{4+5}\right]:{\left(\frac{3}{7}\right)}^7 \\ ={\left(\frac{3}{7}\right)}^9:{\left(\frac{3}{7}\right)}^7={\left(\frac{3}{7}\right)}^{9-7}={\left(\frac{3}{7}\right)}^2 \end{gathered}$$

$$\begin{gathered} b) \left[{\left(\frac{7}{8}\right)}^5:{\left(\frac{7}{8}\right)}^4\right].\frac{7}{8}=\left[{\left(\frac{7}{8}\right)}^{5-4}\right].\frac{7}{8} \\ ={\left(\frac{7}{8}\right)}^1.{\left(\frac{7}{8}\right)}^1={\left(\frac{7}{8}\right)}^{1+1}={\left(\frac{7}{8}\right)}^2 \end{gathered}$$

$$\begin{gathered} c) \left[{\left(0,6\right)}^3.{\left(0,6\right)}^8\right]:\left[{\left(0,6\right)}^7.{\left(0,6\right)}^2\right] \\ =\left[{\left(0,6\right)}^{3+8}\right]:\left[{\left(0,6\right)}^{7+2}\right] \\ ={\left(0,6\right)}^{11}:{\left(0,6\right)}^9 \\ ={\left(0,6\right)}^{11-9}={\left(0,6\right)}^2 \end{gathered}$$