Tìm x, biết: \(\frac{x-7}{20}\)+\(\frac{x-7}{21}\)+\(\frac{x-7}{32}\)-\(\frac{x-7}{23}\)+\(\frac{x-7}{54}\)=0
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\(\frac{7}{x}=\frac{y}{21}=\frac{-42}{54}\)
Ta có : \(\frac{-42}{54}=\frac{-42:6}{54:6}=\frac{-7}{9}\)
+) \(\frac{7}{x}=\frac{-7}{9}\)=> 7.9 = (-7).x => (-7).x = 63 => x = -9
+) \(\frac{y}{21}=\frac{-7}{9}\)=> y.9 = 21.(-7) => y.9 = -147 => y = -49/3
Vậy x = 9,y = -49/3
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Ta có:
\(\frac{x+7}{2010}+\frac{x+6}{2011}=\frac{x+5}{2012}+\frac{x+4}{2013}\)
\(\Leftrightarrow\left(\frac{x+7}{2010}+1\right)+\left(\frac{x+6}{2011}+1\right)=\left(\frac{x+5}{2012}+1\right)+\left(\frac{x+4}{2013}+1\right)\)
\(\Leftrightarrow\frac{x+2017}{2010}+\frac{x+2017}{2011}=\frac{x+2017}{2012}+\frac{x+2017}{2013}\)
\(\Leftrightarrow\left(x+2017\right)\left(\frac{1}{2010}+\frac{1}{2011}\right)=\left(x+2017\right)\left(\frac{1}{2013}+\frac{1}{2014}\right)\)
Suy ra \(x+2017=0\)
Vậy \(x=-2017\)
b) Dễ tự làm nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,x\cdot\frac{1}{2}\cdot\frac{2}{3}=4\)
\(\Rightarrow x\cdot\frac{1}{3}=4\)
\(\Rightarrow x=12\)
\(b,-\frac{2}{7}\cdot\frac{5}{7}\cdot x=\frac{7}{21}\)
\(\Rightarrow-\frac{10}{49}x=\frac{7}{21}\)
\(\Rightarrow x=-\frac{49}{30}\)
k đi làm tiếp cho
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\(\begin{array}{l}a)x - \left( {\dfrac{5}{4} - \dfrac{7}{5}} \right) = \dfrac{9}{{20}}\\x = \dfrac{9}{{20}} + \left( {\dfrac{5}{4} - \dfrac{7}{5}} \right)\\x = \dfrac{9}{{20}} + \dfrac{{25}}{{20}} - \dfrac{{28}}{{20}}\\x = \dfrac{{6}}{{20}}\\x = \dfrac{{ 3}}{{10}}\end{array}\)
Vậy \(x = \dfrac{{ 3}}{{10}}\)
\(\begin{array}{*{20}{l}}{b)9 - x = \dfrac{8}{7} - \left( { - \dfrac{7}{8}} \right)}\\\begin{array}{l}9 - x = \dfrac{8}{7} + \dfrac{7}{8}\\9 - x = \dfrac{{64}}{{56}} + \dfrac{{49}}{{56}}\\9 - x = \dfrac{{113}}{{56}}\end{array}\\{x = 9 - \dfrac{{113}}{{56}}}\\{x = \dfrac{{504}}{{56}} - \dfrac{{113}}{{56}}}\\{x = \dfrac{{391}}{{56}}}\end{array}\)
Vậy \(x = \dfrac{{391}}{{56}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{-x}{21}=\frac{20}{7}\)
\(\Rightarrow-x.7=21.20\)
\(\Rightarrow-x.7=420\)
\(\Rightarrow-x=420:7\)
\(\Rightarrow-x=-60\)
\(\frac{-x}{21}=\frac{20}{7}\)
\(\Rightarrow-x.7=20.21\)
\(\Rightarrow-7x=420\)
\(\Rightarrow x=420:-7\)
\(\Rightarrow x=-60\)
Vậy \(x=-60\)
Chúc bạn học tốt !!!
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1) a) => \(\frac{x}{2}=\frac{y}{5}vàx+y=21\)
Áp dụng tính chất của dãy tỉ số bằng nhau , ta có :
\(\frac{x}{2}=\frac{y}{5}=\frac{x+y}{2+5}=\frac{21}{7}=3\)
* \(\frac{x}{2}=3\Rightarrow x=2\cdot3=6\)
* \(\frac{y}{5}=3\Rightarrow y=3\cdot5=15\)
c) =.> \(\frac{x}{7}=\frac{y}{5}vày-x=12\)
Áp dụng tính chất của dãy tỉ số bằng nhau , ta có :
\(\frac{x}{7}=\frac{y}{5}=\frac{y-x}{5-7}=\frac{12}{-2}=-6\)
*\(\frac{x}{7}=-6\Rightarrow x=-6\cdot7=-42\)
*\(\frac{y}{5}=-6\Rightarrow y=-6\cdot5=-30\)
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\(a,97\times327+327\times3\)
\(=327\times\left(97+3\right)\)
\(=327\times100\)
\(=32700\)
\(b,\frac{1}{7}\times\frac{4}{23}+\frac{1}{7}\times\frac{25}{23}+\frac{1}{7}\times\frac{17}{23}+5\times\frac{1}{7}\)
\(=\frac{1}{7}\times\left(\frac{4}{23}+\frac{25}{23}+\frac{17}{23}+5\right)\)
\(=\frac{1}{7}\times7\)
\(=1\)
a) 97 x 327 + 327 x 3
= (97 + 3) x 327
= 100 x 327 = 32700
b) \(\frac{1}{7}\times\frac{4}{23}+\frac{1}{7}\times\frac{25}{23}+\frac{1}{7}\times\frac{17}{23}+5\times\frac{1}{7}\)
\(=\frac{1}{7}\times\left(\frac{4}{23}+\frac{25}{23}+\frac{17}{23}+5\right)\)
\(=\frac{1}{7}\times7=\frac{7}{7}=1\)
bài này dễ mà
=>(x-7)\(\times\)(\(\frac{1}{20}+\frac{1}{21}+\frac{1}{32}-\frac{1}{23}+\frac{1}{54}\))=0
Mà \(\frac{1}{20}+\frac{1}{21}+\frac{1}{32}-\frac{1}{23}+\frac{1}{54}\)\(\ne\)0
=>x-7=0
=>x=7
Vậy x=7
chúc bn học tốt. nhớ like cho mik nha