Question

tính nhanh : 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64

Answer 1

Đặt \(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)

\(2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)

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

\(A=1-\frac{1}{64}\)

\(A=\frac{63}{64}\)

 

Answer 2

=32/64+14/64+8/64+4/64+2/64+1/64

=32+14+8+4+2+1/64

=61/64

Answer 3

1/2 +1/4+ 1/8+1/16+1/32+1/64

=1/1×2+1/2×2+1/2×4+1/4×4+1/4+8+1/8×8

=1/1-1/2+1/2-1/2+1/2-1/4+1/4-1/4+1/4-1/8+1/8-1/8

=1-1/8

=7/8

Answer 4

1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64

=0.984375

Answer 5

KO BIẾT

Answer 6

2A=1+21​+41​+81​+161​+321​

2�−�=(1+12+14+18+116+132)−(12+14+18+116+132+164)2A−A=(1+21​+41​+81​+161​+321​)−(21​+41​+81​+161​+321​+641​)

�=1−164A=1−641​

�=6364A=6463​