Question

como eu respondo ??$5^-^{2} \cdot 8^-^{2}$

Answer 1

Há, pelo menos, duas formas:

1ª:

      $5^{-2}~.~8^{-2}=\\\\=\left(\frac{1}{5}\right)^{2}~.~\left(\frac{1}{8}\right)^2\\\\=\frac{1^2}{5^2}~.~\frac{1^2}{8^2}\\\\=\frac{1}{25}~.~\frac{1}{64}\\\\=\frac{1~.~1}{25~.~64}\\\\=\boxed{\frac{1}{1600}}$

2ª:

      $5^{-2}~.~8^{-2}=\\\\=\left(5~.~8\right)^{-2}\\\\=\left(40\right)^{-2}\\\\=\left(\frac{1}{40}\right)^{2}\\\\=\frac{1^2}{40^2}\\\\=\boxed{\frac{1}{1600}}$