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2: \(=\dfrac{0.8}{\dfrac{16}{25}-\dfrac{1}{25}}+\dfrac{\dfrac{71}{75}\cdot\dfrac{7}{4}}{\dfrac{119}{36}\cdot\dfrac{36}{17}}\)
\(=\dfrac{4}{5}\cdot\dfrac{5}{3}+\dfrac{71}{300}=\dfrac{471}{300}=\dfrac{157}{100}\)
3: \(=\dfrac{\dfrac{2}{5}-\dfrac{2}{9}+\dfrac{2}{11}}{\dfrac{7}{5}-\dfrac{7}{9}+\dfrac{7}{11}}-\dfrac{\dfrac{2}{6}-\dfrac{2}{8}+\dfrac{2}{10}}{\dfrac{7}{6}-\dfrac{7}{8}+\dfrac{7}{10}}\)
=2/7-2/7=0
1.
a.= (-5/24+3/4+7/12): -9/4
=(-5/24+18/24+14/24) . -4/9
= 9/8 .-4/9=-1/2
b. =(3/5+83/200-3/200).8/3 .1/4
=(120/200+83/200-3/200) .2/3
=1.2/3=2/3
2.
a. 1/3(2x-5)=-2/3-3/2
1/3(2x-5)=-13/6
2x-5=-13/2
2x=-3/2
x=-3/2:2=-3/4
b. 1/3x-1/2x=3/4
x(1/3-1/2)=3/4
x.1/6=3/4
x=9/2
\(\Rightarrow A=\left(\frac{\frac{2}{5}-\frac{2}{9}+\frac{2}{11}}{\frac{7}{5}-\frac{7}{9}+\frac{7}{11}}-\frac{\frac{1}{3}-\frac{1}{4}+\frac{1}{5}}{1+\frac{1}{6}-\frac{7}{8}+\frac{7}{10}}\right):\frac{2014}{2015}\)
\(\Rightarrow A=\left(\frac{2\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{11}\right)}{7\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{11}\right)}-\frac{\frac{17}{60}}{\frac{119}{120}}\right):\frac{2014}{2015}\)
\(\Rightarrow A=\left(\frac{2}{7}-\frac{2}{7}\right):\frac{2014}{2015}\)
\(\Rightarrow A=0:\frac{2014}{2015}\Rightarrow A=0\)
= A . ( \( {1 \over 3}\) - \( {1 \over 4}\) - \( {1 \over 12}\) ) = A . ( \( {1 \over 12}\) - \({1 \over 12}\) ) = A . 0 = 0
\(\frac{1}{2}\cdot\left(2-x\right)+0,25=x-\frac{5}{2}:0,4+3\)
\(=>\frac{1}{2}\cdot2-\frac{1}{2}x+\frac{1}{4}=x-\frac{5}{2}:\frac{2}{5}+3\)
\(=>1+\frac{1}{4}+\frac{5}{2}\cdot\frac{5}{2}-3=x-\frac{1}{2}x\)
\(=>\frac{4}{4}+\frac{1}{4}+\frac{25}{4}-\frac{12}{4}=\frac{x}{2}\)
\(=>\frac{18}{4}=\frac{x}{2}\)
\(=>\frac{x}{2}=\frac{9}{2}\)
\(=>x=9\)
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\(\frac{1}{2}\left(2-x\right)+0,25=x-\frac{5}{2}:0,4+3\)
<=> 1-0,5x+0,25=x-6,25+3
<=> 1,5x=1+0,25+6,25-3=4,5
<=> x=4,5:1,5=3
vậy x=3