Respuesta :
[tex]8^{-\tfrac 23}\\\\\\=\left(8^{\tfrac 13 }\ \right)^{-2}\\\\\\=\left[\left(2^3\right)^{\tfrac 13} \right]^{-2}\\\\\\=\left(2^{\tfrac 33} \right)^{-2}\\\\\\=2^{-2}\\\\=\dfrac 1{2^2}\\\\\\=\dfrac 14[/tex]
[tex] {8}^{ - \frac{2}{3} } \\ = {2}^{3 \times - \frac{2}{3} } \\ = {2}^{ - 2} \\ = \frac{1}{2^{ 2}} \\ = \frac{1}{4} [/tex]
Hope you could get an idea from here.
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