1/2+1/4+1/8+1/16+1/32+1/64+1/128
=1/1-1/2+1/2-1/4+1/4-1/8+1/8-1/16+1/16-1/32+1/32-1/64+1/64-1/128
=1/1-1/28
=128/128-1/128
=127/128
X*[1/2+1/4+1/8+1/16+1/32+1/64+1/128]=127/128
tính nhanh p/s 1+ 5/4 + 5/8 + 5/16 + 5/32 + 5/64
b) 1/3 +1/9 + 1/27 + 1/81 +...........+ 1/59049
c) 3/2 + 3/8 + 3/32 +3/128 + 3/512
d) 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 giúp mình với 
C = 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
1/2+1/4+1/8+1/16+1/32+1/64+1/128
1/2+1/4+1/8+1/16+1/32+1/64+1/128
1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
1\2+1\4+1\8+1\16+1\32+1\64+1\128
1:2+1:4+1:8+1:16+1:32+1:64+1:128
e =1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
