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a: \(=3\cdot\dfrac{6+14-9}{42}\cdot\dfrac{14}{11}\)
\(=3\cdot\dfrac{11}{42}\cdot\dfrac{14}{11}=1\)
b: \(=\dfrac{19}{5}\cdot\dfrac{11}{10}+\dfrac{9}{5}\cdot\dfrac{7}{3}\)
\(=\dfrac{209}{50}+\dfrac{63}{15}=4.18+4.2=8,38\)
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\(\left(\frac{5}{7}-x\right)\times\frac{14}{5}=\frac{7}{10}+\frac{1}{2}\)
\(\left(\frac{5}{7}-x\right)\times\frac{14}{5}=\frac{6}{5}\)
\(\frac{5}{7}-x=\frac{6}{5}:\frac{14}{5}\)
\(\frac{5}{7}-x=\frac{3}{7}\)
\(x=\frac{5}{7}-\frac{3}{7}\)
\(x=\frac{2}{7}\)
x=2/7
bài này lớp 4
mình đã học rồi
cho lên bay giờ mình quen rùi
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( 5/7 - y ) * 14/5 = 7/10 + 1/2
( 5/7 - y ) x 14/5 = 6/5
5/7 - y = 6/5 : 14/5
5/7 - y = 3/7
y = 5/7 - 3/7
y = 2/7
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\(\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\frac{7}{10}+\frac{1}{2}=\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\left(\frac{5}{7}-y\right)\cdot\frac{14}{5}=\frac{6}{5}\)\(\frac{6}{5}\)
\(=>\frac{5}{7}-y=\frac{6}{5}\) / \(\frac{14}{5}=\frac{5}{7}-y=\frac{3}{7}=\frac{5}{7}-\frac{3}{7}=\frac{2}{7}\)
\(=>y=\frac{2}{7}\)
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\(10+12+14+...+198+200\) có \(\left(200-10\right):2+1=96\)( số hạng )
\(10+12+14+...+198+200\)\(=\left(200+10\right)\times96:2=10080\)
\(\frac{1}{5\times7}+\frac{1}{7\times9}+...+\frac{1}{1011\times2013}\)
\(=\frac{1}{2}\times\left(\frac{1}{5}-\frac{1}{7}\right)+\frac{1}{2}\times\left(\frac{1}{7}-\frac{1}{9}\right)+...+\frac{1}{2}\times\left(\frac{1}{2011}-\frac{1}{2013}\right)\)
\(=\frac{1}{2}\times\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{2011}-\frac{1}{2013}\right)\)
\(=\frac{1}{2}\times\left(\frac{1}{5}-\frac{1}{2013}\right)\)
\(=\frac{1}{2}\times\frac{2008}{10065}\)
\(=\frac{1004}{10065}\)
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138/35
mk nha
mk nhanh
k bn
thanks trc
\(\frac{7}{5}+\frac{1}{7}+\frac{14}{10}+1\)
\(=\frac{7}{5}+\frac{7}{5}+\frac{1}{7}+1\)
\(=\frac{14}{5}+\frac{1}{7}+1\)
\(=\frac{14}{5}+\frac{8}{7}=\frac{138}{135}\)