Question

so sánh: 1/2 - 1/4 - 1/8 - 1/16- 1/32 - 1/64 - 1/128 

so vs 1 

Answer 1

\(\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}-\frac{1}{64}-\frac{1}{128}\)

\(=\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\right)-2\times\left(\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\right)\)

\(=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}-\frac{1}{64}\)

\(=\frac{1}{128}\)< 1

Answer 2

còn 1 cách nữa mk lm nhưng ko chắc nên hỏi

1/2-(1/4+1/8+1/32+1/64+1/128)

=1/2-(1/2-1/4+1/4-1/8+1/8-1/32+1/32-1/64+1/64-1/128)

=1/2-(1/2-1/128)

=1/2-63/128

=1/128