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5A = 5/3.8 + 5/8.13 + 5/13.18 + ... + 5/33.38
= 1/3 - 1/8 + 1/8 - 1/13 + ... + 1/33 - 1/38
= 1/3 - 1/38
5A = 35/114
=> A = 35/114 : 5 = 7/144
7B = 7/3.10 + 7/10.17 + ... + 7/31.38
= 1/3 - 1/10 + 1/10- 1/17 + .. + 1/31 - 1/38
= 1/3 - 1/38
B = 35/144 : 7 = 5/144
VẬy A> B
Ta có: *)A.5=5(1/3.8+1/8.13+...+1/33.38)
=5/3.8+5/8.13+...+5/33.38
=1/3-1/8+1/8-1/13+...+1/33-1/38
=1/3-1/38
=> A=(1/3-1/38).1/5
*)7B=7/3.10+7/10.17+7/17.24+...+7/31.38
=1/3-1/10+1/10-1/17+...+1/31-1/38
=1/3-1/38
=>B=(1/3-1/38).1/7
Do đó a/b=(1/5)/(1/7)=7/5
k mk nha!
1/3.10+1/10.17+......+1/73.80 - 1/2.9 - 1/9.16 - 1/16.23 - 1/23.30
= (7/3.10+7/10.17+......+7/73.80) : 7 - (7/2.9 + 7/9.16 + 7/16.23 + 7/23.30) : 7
= (1/3-1/10+1/10-1/17+...+1/73-1/80) : 7 - (1/2-1/9+1/9-1/16+1/16-1/23+1/23-1/30) : 7
=(1/3-1/80) : 7 - (1/2-1/30) : 7
= 77/240 : 7 - 7/15 : 7
=11/240 - 1/15
= -1/48
Nhấn đúng cho mk nha!!!!!!!!!!!!!
\(\frac{1}{3.8}+\frac{1}{8.13}+...+\frac{1}{2018.2023}\)
Ta có : \(\frac{1}{3.8}+\frac{1}{8.13}+...+\frac{1}{2018.2023}\)
\(=\frac{1}{5}.\left(\frac{5}{3.8}+\frac{5}{8.13}+...+\frac{5}{2018.2023}\right)\)
\(=\frac{1}{5}.\left(\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+...+\frac{1}{2018}-\frac{1}{2023}\right)\)
\(=\frac{1}{5}.\left(\frac{1}{3}-\frac{1}{2023}\right)\)
\(=\frac{1}{5}.\frac{2020}{6069}=\frac{404}{6069}\)
A=\((\frac{1}{3.8}+\frac{1}{8.13}+...+\frac{1}{33.38})\)
A=\(\frac{1}{5}\left(\frac{5}{3.8}+\frac{5}{8.13}+...+\frac{5}{33.38}\right)\)
A=\(\frac{1}{5}\left(\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+...+\frac{1}{33}-\frac{1}{38}\right)\)
A=\(\frac{1}{5}.\left(\frac{1}{3}-\frac{1}{38}\right)\)
A=\(\frac{1}{5}.\frac{35}{114}\)
A=\(\frac{7}{114}\)
B=\((\frac{1}{3.10}+\frac{1}{10.17}+...+\frac{1}{31.38})\)
B=\(\frac{1}{7}\left(\frac{7}{3.10}+\frac{7}{10.17}+...+\frac{7}{31.38}\right)\)
B=\(\frac{1}{7}\left(\frac{1}{3}-\frac{1}{10}+\frac{1}{10}-\frac{1}{17}+...+\frac{1}{31}-\frac{1}{38}\right)\)
B=\(\frac{1}{7}\left(\frac{1}{3}-\frac{1}{38}\right)\)
B=\(\frac{1}{7}.\frac{35}{114}\)
B=\(\frac{5}{114}\)
⇒ \(\frac{A}{B}\)=\(\frac{7}{114}:\frac{5}{114}=\frac{7}{114}.\frac{114}{5}=\frac{7}{5}\)
Vậy \(\frac{A}{B}=\frac{7}{5}\)
A = \(\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+....+\frac{1}{33}-\frac{1}{38}\)
=\(\frac{1}{3}-\frac{1}{38}\)
=\(\frac{35}{114}\)
B =\(\frac{1}{3}-\frac{1}{10}+\frac{1}{10}-\frac{1}{17}+...+\frac{1}{31}-\frac{1}{38}\)
=\(\frac{1}{3}-\frac{1}{38}\)
=\(\frac{35}{114}\)
=>tỉ số \(\frac{A}{B}\)= \(\frac{35}{114}:\frac{35}{114}\)=1
A=1/3.8+1/8.13+1/13.18+...+1/33.38
5A=5/3.8+5/8.13+5/13.18+...+5/33.38
5A=1/3-1/8+1/8-1/13+1/13-1/18+...+1/33-1/38
5A=1/3-1/38
5A=38/114-3/114
5A=35/114
A=35/114:5
A=7/114
B=1/3.10+1/10.17+1/17.24+1/24.31+1/31.38
7B=7/3.10+7/10.17+7/17.24+7/24.31+7/31.38
7B=1/3-1/10+1/0-1/17+1/17-1/24+1/24-1/31+1/31-1/38
7B=1/3-1/38
7B=38/114-3/114
7B=35/114
B=35/114:7
B=5/114