Question

O valor da expressão

2^-1 + 2^-2 / 2^-3

a)3/32
b) 6
c) 1
d) 2
e) 3

Answer 1

Quando temos expoente negativo, para tirar o sinal basta inverter a fração:

$\frac{2^{-1}+2^{-2}}{2^{-3}} \\\\ \frac{\frac{1}{2}+(\frac{1}{2})^{2}}{(\frac{1}{2})^{3}} \\\\ \frac{\not \frac{1}{2} \cdot (1+\frac{1}{2})}{\not (\frac{1}{2})^{3}} \\\\ \frac{1+\frac{1}{2}}{(\frac{1}{2})^{2}} \\\\ \frac{\frac{3}{2}}{\frac{1}{4}} = \frac{3 \cdot 4}{1 \cdot 2} = \frac{12}{2} = \boxed{6}$

Alternativa B,