Tìm x, biết: a) (-5/9)^10 : x = (-5/9)^8 b) x : (-5/9)^8 = (-9/5)^8

* Hướng dẫn giải

a) Điều kiện $x\ne 0$

$$\begin{gathered} {\left(\frac{-5}{9}\right)}^{10}:x={\left(\frac{-5}{9}\right)}^8 \\ \iff x={\left(\frac{-5}{9}\right)}^{10}:{\left(\frac{-5}{9}\right)}^8 \\ \iff x={\left(\frac{-5}{9}\right)}^2 \\ \iff x=\frac{25}{81} \left(t/m\right) \end{gathered}$$

b)