7] Calcule as seguintes potências. a) (-2)^-2 d) (0,999ldots )^-3 b) -((1)/(2))^-4 e) 3^-2 c) (-3)^-2

a) $$(-2)^{-2} = \frac{1}{(-2)^2} = \frac{1}{4}$$
$$(0,999\ldots )^{-3} = \frac{1}{(0,999\ldots )^3} = \frac{1}{0,997001} \approx 1,003$$

b) $$-(\frac {1}{2})^{-4} = -(\frac{2}{1})^4 = -16$$

e) $$3^{-2} = \frac{1}{3^2} = \frac{1}{9}$$

c) $$(-3)^{-2} = \frac{1}{(-3)^2} = \frac{1}{9}$$