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\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\)
\(=\frac{1x64}{2x64}+\frac{1x32}{4x32}+\frac{1x16}{8x16}+\frac{1x8}{16x8}+\frac{1x4}{32x4}+\frac{1x2}{64x2}+\frac{1}{128}\)
\(=\frac{64}{128}+\frac{32}{128}+\frac{16}{128}+\frac{8}{128}+\frac{4}{128}+\frac{2}{128}+\frac{1}{128}\)
\(=\left(\frac{64}{128}+\frac{1}{128}\right)+\left(\frac{32}{128}+\frac{8}{128}\right)+\left(\frac{16}{128}+\frac{4}{128}\right)\)
\(=\frac{65}{128}+\frac{40}{128}+\frac{20}{128}\)
\(=125\)
toán 6 nha:
A=1/2+1/4+1/8+1/16+1/32+1/64+1/28
1/128+A=1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/128
1/128+A=1/2+1/4+1/8+1/16+1/32+1/64+1/64
1/128+A=1/2+1/4+1/8+1/16+1/32+1/32
1/128+A=1/2+1/4+1/8+1/16+1/16
1/128+A=1/2+1/4+1/8+1/8
1/128+A=1/2+1/4+1/4
1/128+A=1/2+1/2
1/128+A=1
A=1-1/128
a=127/128
2A=1+1/2+1/4+1/8+1/16+1/32+1/64
2A-A=(1+1/2+1/4+1/8+1/16+1/32+1/64)-(1/2+1/4+1/8+1/16+1/32+1/64+1/128)
A=1-1/128
A=127/128
A = 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
suy ra: 2A = 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64
2A - A = 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 - 1/2 - 1/4 - 1/8 - 1/16 - 1/32 - 1/64 - 1/128
A = 1 - 1/128 = 127/128
hok tốt
a×1/2+a×1/6+a×1/12
vơi a =8
\(\Rightarrow\)8×1/2+8×1/6+8×1/12=8×(1/2×1/6+1/12)=8×3/4=6
\(\frac{9}{2}-\frac{8}{3}:\frac{2}{3}+\frac{1}{2}=\frac{9}{2}-4+\frac{1}{2}=\frac{1}{2}+\frac{1}{2}=1\)
\(\frac{12}{5}:\frac{4}{7}-\frac{1}{2}=\frac{21}{5}-\frac{1}{2}=\frac{37}{10}\)
A) 9/2 - 8/3 : 2/3 + 1/2 = 9/2 - 8/3 x 3/2 + 1/2
= 9/2 - 4 + 1/2
= 1/2 + 1/2
= 1.
B) 12/5 : 4/7 - 1/2 = 12/5 x 7/4 - 1/2
= 21/5 -1/2
= 21/10.
\(\frac{2}{3}+\frac{3}{4}:\frac{6}{7}+\frac{1}{8}\cdot\frac{4}{3}\)
\(=\frac{2}{3}+\frac{3}{4}\cdot\frac{7}{6}+\frac{1}{8}\cdot\frac{4}{3}\)
\(=\frac{2}{3}+\frac{21}{24}+\frac{4}{24}\)
\(=\frac{16}{24}+\frac{21}{24}+\frac{4}{24}\)
\(=\frac{37}{24}+\frac{4}{24}\)
\(=\frac{41}{24}\)
2/3 + 3/4 : 6/7 + 1/8 x 4/3 = 2/3 + 7/8 + 1/6
= 16/24 + 21/24 + 4/24
= 41/24