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\(B=\frac{4}{7\cdot31}+\frac{6}{7\cdot41}+\frac{9}{10\cdot41}+\frac{10}{10\cdot57}\)
B/5 = 4/5*7*31 + 6/5*7*41 + 9/5*10*410+7/5*10*57
B/5=4/31*35+6/35*41+9/41*50+7/50*57
B/5= 1/31-1/35+1/35-1/41+1/41-1/50+1/50-1/57
B/5=1/31-1/57
B/5=26/1767
B=130/1767
Vậy B = 130/1767
\(M=\frac{32}{323}\) \(N=\frac{86}{589}\) \(\frac{M}{N}=\frac{496}{731}\)
bài 1 a)
\(\frac{15}{7}\times\frac43+\frac63\)
=\(\frac{60}{21}+\frac63\)
=\(\frac{60}{21}+\frac{42}{21}\)
=\(\frac{102}{21}\)
=\(\frac{34}{7}\)
b)\(\frac{-13}{41}\times\frac{17}{11}\times\frac{11}{17}\)
=\(\frac{-13}{41}\times\left(\frac{17}{11}\times\frac{11}{17}\right)\)
=\(\frac{-13}{41}\times1\)
=\(\frac{-13}{41}\)
a)\(=\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)
\(=\left(\frac{-3}{7}+\frac{3}{7}\right)-\left(\frac{15}{26}+\frac{2}{13}\right)\)
\(=0-\frac{19}{26}\)
\(=-\frac{19}{26}\)
c)\(=\frac{-11}{23}.\left(\frac{6}{7}+\frac{8}{7}\right)-\frac{1}{23}\)
\(=\frac{-11}{23}.2-\frac{1}{23}\)
\(=\frac{-22}{23}-\frac{1}{23}\)
\(=-1\)
Bài 1:
\(g.\frac{5}{11}+\frac{6}{11}=\frac{5+6}{11}=\frac{11}{11}=1\)\(\)
\(e.\frac{-17}{25}.\frac{20}{33}+\frac{-17}{25}.\frac{13}{33}+\frac{-3}{25}=\frac{-17}{25}.\left(\frac{20}{33}+\frac{13}{33}\right)+\frac{-3}{25}\)
\(=\frac{-17}{25}.1+\frac{-3}{25}=\frac{-17}{25}+\frac{-3}{25}=\frac{-17-3}{25}=\frac{-20}{25}=\frac{-4}{5}\)
\(d.\frac{5}{7}.\frac{19}{23}+\frac{5}{7}.\frac{5}{23}-\frac{5}{7}.\frac{1}{23}=\frac{5}{7}\left(\frac{19}{23}+\frac{5}{23}-\frac{1}{23}\right)\)
\(=\frac{5}{7}\left(\frac{19+5-1}{23}\right)=\frac{5}{7}.1=\frac{5}{7}\)
\(c.\left(-11\right).\frac{9}{22}=\frac{\left(-11\right).9}{22}=\frac{-99}{22}=\frac{-9}{2}\)
\(b.\frac{5}{6}-\frac{1}{8}=\frac{5.4}{6.4}-\frac{1.3}{8.3}=\frac{20}{24}-\frac{3}{24}=\frac{17}{24}\)
\(a.\frac{2}{3}+\frac{1}{5}-\frac{1}{6}=\frac{2.10}{3.10}+\frac{1.6}{5.6}-\frac{1.5}{6.5}=\frac{20}{30}+\frac{6}{30}-\frac{5}{30}\)
\(=\frac{20+6-5}{30}=\frac{21}{30}=\frac{7}{10}\)
Bài 2:
\(a.\frac{3}{4}+x=\frac{11}{12}\)
\(\Leftrightarrow x=\frac{11}{12}-\frac{3}{4}\)
\(\Leftrightarrow x=\frac{11}{12}-\frac{9}{12}\)
\(\Leftrightarrow x=\frac{2}{12}=\frac{1}{6}\)
\(b.x-\frac{11}{12}=0,5\)
\(\Leftrightarrow x=\frac{1}{2}-\frac{11}{12}\)
\(\Leftrightarrow x=\frac{6}{12}+\frac{11}{12}\)
\(\Leftrightarrow x=\frac{17}{12}\)
A=4/1.31+6/7.41+9/9.41+ 7/10.57
=20/35.31+30/35.41+45/45.41+35/50.57
=5(4/35.31+6/35.41+9/45.41+7/50.57)
=5(1/31-1/35+1/35-1/41+1/41-1/45+1/45-1/50+1/50-1/57)
=5(1/31-1/57)
B thì làm tương tự nhưng nhân với 2=> B=2(1/31-1/57)
=> A/B=5/2
A/B=5/2
Ai tk mình, mình k lại
Cảm ơn nhưng mình cần lời giải đầy đủ bạn ạ.
Xét A
Ta có : A = \(\frac{1}{5}\)x \(\frac{4}{31\cdot35}\)+ \(\frac{1}{5}\)x \(\frac{6}{35\cdot41}\)+ \(\frac{1}{5}\)x \(\frac{9}{41\cdot50}\)+ \(\frac{1}{5}\)x \(\frac{7}{50\cdot57}\)
A = \(\frac{1}{5}\)x (\(\frac{4}{31\cdot35}\)+ \(\frac{6}{35\cdot41}\)+ \(\frac{9}{41\cdot50}\)+ \(\frac{7}{50\cdot57}\))
A = 1/5 x ( 1/31 - 1/35 + 1/35 - 1/41 + 1/41 - 1/50 + 1/50 - 1/57 )
A = 1/5 x ( 1/31 - 1/57 )
Xét B
Ta có B = ...
( nhân với 1/2 rồi bạn tự làm nha )
( Good luck )
\(\frac{1}{5}A=\frac{4}{31.35}+....+\frac{7}{50.57}\)
\(\frac{1}{5}A=\frac{1}{31}-\frac{1}{35}+...+\frac{1}{50}-\frac{1}{57}\)
\(\frac{1}{5}A=\frac{1}{31}-\frac{1}{57}=\frac{26}{1767}\)
\(A=\frac{26}{\frac{1767}{\frac{1}{5}}}=\frac{130}{1767}\)
\(\frac{1}{2}B=\frac{7}{31.38}+....+\frac{11}{46.57}\)
\(\frac{1}{2}B=\frac{1}{31}-\frac{1}{38}+..+\frac{1}{46}-\frac{1}{57}\)
\(\frac{1}{2}B=\frac{1}{31}-\frac{1}{57}=\frac{26}{1767}\)
\(B=\frac{\frac{26}{1767}}{\frac{1}{2}}=\frac{52}{1767}\)
\(\frac{A}{B}=\frac{130}{\frac{1767}{\frac{52}{1767}}}=\frac{5}{2}\)