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giúp mik nha chiều này 6:00 mik nộp rồi
ai nhanh mik sẽ k cho 3 k
\(2\frac{3}{5}x-\frac{1}{7}=1\frac{9}{35}\)
\(\frac{13}{5}x=\frac{44}{35}+\frac{1}{7}\)
\(\frac{13}{5}x=\frac{7}{5}\)
\(x=\frac{7}{5}:\frac{13}{5}\\ x=\frac{7}{13}\)
1)C= 1/5+1/10+1/20+1/40+...+1/1280
\(=\frac{1}{5}\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}\right)\)
Đặt cái trong ngoặc là A ta có:\(2A=2+1+...+\frac{1}{2^7}\)
\(2A-A=\left(2+1+...+\frac{1}{2^7}\right)-\left(1+\frac{1}{2}+...+\frac{1}{2^8}\right)\)
\(A=2-\frac{1}{2^8}\).Thay A vào ta được:\(C=\frac{1}{5}\left(2-\frac{1}{2^8}\right)=\frac{1}{5}\cdot\frac{511}{256}=\frac{511}{1280}\)
2)D= 2/1*3+2/3*5+2/5*10+2/7*9+2/9*11+2/11*18+2/13*15
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{13}-\frac{1}{15}\)
\(=1-\frac{1}{15}\)
\(=\frac{14}{15}\)
3)E= 4/3*7+4/7*11+4/11*15+4/15*19+4/19*23+4/23*27
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
4)G= 1/2+1/6+1/12+1/20+1/30+1/42+...+1/110
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{10.11}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{10}-\frac{1}{11}\)
\(=1-\frac{1}{11}\)
\(=\frac{10}{11}\)
5)H= 3/1*2+3/2*3+3/3*4+3/4*5+...+3/9*10
\(=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=3\left(1-\frac{1}{10}\right)\)
\(=3\times\frac{9}{10}\)
\(=\frac{27}{10}\).Lần sau bạn đăng ít một thôi nhé
a/ \(\frac{\left(-3\right)}{5}+\frac27\)
\(=\frac{-21}{35}+\frac{10}{35}\)
\(=-\frac{11}{35}\)
b/ \(\frac{\left(-4\right)}{7}+\frac35\)
\(=\frac{-20}{35}+\frac{21}{35}\)
\(=\frac{1}{35}\)
c/\(\frac{\left(-13\right)}{17}-\frac{2}{11}-\frac{\left(-13\right)}{17}-\frac{9}{11}\)
\(=\frac{\left(-13\right)}{17}+\left(-\frac{2}{11}-\frac{9}{11}\right)\)
\(=\frac{\left(-13\right)}{17}-1\)
\(=\frac{\left(-13\right)}{17}-\frac{17}{17}\)
\(\equiv-\frac{22}{19}\)
d/\(\frac{\left(-3\right)}{19}-\frac27-\frac{\left(-3\right)}{19}-\frac57\)
\(=\frac{\left(-3\right)}{19}+\left(\frac{-2}{7}-\frac57\right)\)
\(=\frac{\left(-3\right)}{19}-1\)
\(=\frac{\left(-3\right)}{19}-\frac{19}{19}\)
\(=\frac{-22}{19}\)
= (-13)/17 . (2/11 + 9/11)
= (-13)/17 . 1
= -13/17 d) (-3)/19 . 2/7 + (-3)/19 . 5/7
= (-3)/19 . (2/7 + 5/7)
= (-3)/19 . 1
= -3/19