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\(=1-\dfrac{1}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+....+\dfrac{1}{995}-\dfrac{1}{997}+\dfrac{1}{997}-\dfrac{1}{999}\right)\)
\(=1-\dfrac{1}{2}\cdot\dfrac{998}{999}=1-\dfrac{499}{999}=\dfrac{500}{999}\)
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a) 6/-x=x/-24
=> -x.x=6.-24
=>-x.x=-144
=>x=12 hay x=-12
b)9/x=-35/105
=>9/x=-1/3
=>x=9.3/-1=-27
=>x=-27
c)x-1/8=5/8
=>x=5/8+1/8
=>x=3/4
d)x-1/2-(3/2+x)=-2
=>-x+4/2=-2
=>-x/2=0
=>x=0
e)x+1/3=-12/5.10/6
x+1/3=-4
x=-4-1/3
x= -13/3
#YM
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3/7 + 1/2 - 17/7 +3/2
=(1/2+3/2) + (3/7-17/7)
=2+-2
=0
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1574+(625-x)=2023
⇒ 625-x=2023-1574=449
⇒ x=625-449=176
Vậy x=176
1574 + (625 - x) = 2023
625 - x = 2023 - 1574
625 - x = 449
x = 625 - 449
x = 176
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\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)
\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)
\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)
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`@` `\text {Ans}`
`\downarrow`
`a)`
\(\left(\dfrac{7}{8}-\dfrac{3}{4}\right)\cdot1\dfrac{1}{3}-\dfrac{2}{3}\cdot0,5\)
`=`\(\dfrac{1}{8}\cdot\dfrac{4}{3}-\dfrac{1}{3}\)
`=`\(\dfrac{1}{6}-\dfrac{1}{3}=-\dfrac{1}{6}\)
`b)`
\(\left(2+\dfrac{5}{6}\right)\div1\dfrac{1}{5}+\left(-\dfrac{7}{12}\right)\)
`=`\(\dfrac{17}{6}\div1\dfrac{1}{5}-\dfrac{7}{12}\)
`=`\(\dfrac{85}{36}-\dfrac{7}{12}=\dfrac{16}{9}\)
`c)`
\(75\%-1\dfrac{1}{2}+0,5\div\dfrac{5}{12}\)
`=`\(-\dfrac{3}{4}+\dfrac{6}{5}=\dfrac{9}{20}\)
a) \(\left(\dfrac{7}{8}-\dfrac{3}{4}\right).1\dfrac{1}{3}-\dfrac{2}{3}.0,5\)
\(=\left(\dfrac{7}{8}-\dfrac{6}{8}\right).\dfrac{4}{3}-\dfrac{2}{3}.\dfrac{1}{2}\)
\(=\dfrac{1}{8}.\dfrac{4}{3}-\dfrac{2}{3}.\dfrac{1}{2}\)
\(=\dfrac{1}{6}-\dfrac{1}{3}\)
\(=\dfrac{-1}{6}\)
b) \(\left(2+\dfrac{5}{6}\right):1\dfrac{1}{5}+\dfrac{-7}{12}\)
\(=\left(\dfrac{12}{6}+\dfrac{5}{6}\right):\dfrac{6}{5}+\dfrac{-7}{12}\)
\(=\dfrac{17}{6}.\dfrac{5}{6}+\dfrac{-7}{12}\)
\(=\dfrac{85}{36}+\dfrac{-7}{12}\)
\(=\dfrac{16}{9}\)
c) \(75\%-1\dfrac{1}{2}+0,5:\dfrac{5}{12}\)
\(=\dfrac{3}{4}-\dfrac{3}{2}+\dfrac{1}{2}.\dfrac{12}{5}\)
\(=\dfrac{3}{4}-\dfrac{6}{4}+\dfrac{6}{5}\)
\(=\dfrac{-3}{4}+\dfrac{6}{5}\)
\(=\dfrac{9}{20}\)
a: \(\dfrac{1}{4}+\dfrac{3}{4}:\left(-\dfrac{6}{7}\right)\)
\(=\dfrac{1}{4}+\dfrac{3}{4}\cdot\dfrac{-7}{6}\)
\(=\dfrac{1}{4}+\dfrac{-7}{8}\)
\(=\dfrac{2}{8}-\dfrac{7}{8}=-\dfrac{5}{8}\)
c: \(\dfrac{5}{6}+\dfrac{1}{6}:\left(-3\right)\)
\(=\dfrac{5}{6}-\dfrac{1}{18}\)
\(=\dfrac{15}{18}-\dfrac{1}{18}=\dfrac{14}{18}=\dfrac{7}{9}\)
g: \(\left(\dfrac{3}{3}+\dfrac{-1}{3}-\dfrac{5}{8}\right):\dfrac{-5}{6}\)
\(=\left(\dfrac{2}{3}-\dfrac{5}{8}\right):\dfrac{-5}{6}\)
\(=\dfrac{16-15}{24}\cdot\dfrac{6}{-5}\)
\(=\dfrac{1}{4}\cdot\dfrac{1}{-5}=\dfrac{1}{-20}\)
h: \(\left(-\dfrac{2}{5}+\dfrac{1}{4}\right):\left(1-\dfrac{2}{5}\right)\)
\(=\dfrac{-2\cdot4+5}{20}:\dfrac{3}{5}\)
\(=\dfrac{-3}{20}\cdot\dfrac{5}{3}=\dfrac{-1}{4}\)
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