Đặt A=1+2+4+...+128=1+2+22+...+27
=>2A=2+22+23+...+28
=>2A+1=1+2+22+...+27+28=A+28
=>2A-A=28-1
A=256-1
A=255
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Đặt A=1+2+4+...+128=1+2+22+...+27
=>2A=2+22+23+...+28
=>2A+1=1+2+22+...+27+28=A+28
=>2A-A=28-1
A=256-1
A=255
tính nhanh 2+4+8+16+32+64+128+256
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
Tính nhanh :
1/2+1/4+1/8+1/16+1/32+1/64+1/128
Tính nhanh
1/2 + 1/4 + 1/8 + 1/16 +1/32 + 1/64 + 1/128
Tính nhanh:
1/2+1/4+1/8+1/16+1/32+1/64+1/128
Tính nhanh : 1+1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512
Tính nhanh
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256
Tính nhanh:
1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
tinh nhanh
1/4+1/8+1/16+1/32+1/64+1/128