$\frac{1}{4}$ + $\frac{1}{8}$ + $\frac{1}{16}$ + $\frac{1}{32}$ + $\frac{1}{64}$ + $\frac{1}{128}$
=$\frac{1}{2}$ - $\frac{1}{4}$ + $\frac{1}{4}$ - $\frac{1}{8}$ + $\frac{1}{8}$ - $\frac{1}{16}$ + $\frac{1}{16}$ - $\frac{1}{32}$ + $\frac{1}{32}$ - $\frac{1}{64}$ + $\frac{1}{64}$ - $\frac{1}{128}$
= $\frac{1}{2}$ - $\frac{1}{128}$
= $\frac{63}{128}$
Chúc bạn học tốt ^^