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    27 tháng 7 2018

    1.Vì  \(\frac{x}{-2}=\frac{-8}{x}\Rightarrow-2.\left(-8\right)=x.x\)

                                            \(16=x.x\)hay \(4^2=x^2\Rightarrow x=4\)

    2. Rút gọn : \(\frac{20}{28}=\frac{5}{7}=\frac{-5}{-7}\)

    \(\Rightarrow x=-7\)

    3. \(\frac{x}{2}-\frac{11}{5}=\frac{7}{8}\times\frac{64}{49}\)

    \(\frac{x}{2}-\frac{11}{5}=\frac{8}{7}\)

    Mà \(\frac{8}{7}+\frac{11}{5}=\frac{502}{35}\)

    \(\Rightarrow x=\frac{234}{35}\)

    27 tháng 7 2018

    1) \(\frac{x}{-2}=\frac{-8}{x}\)

    \(\Rightarrow x\times x=\left(-2\right)\times\left(-8\right)\)

    \(\Rightarrow x^2=16\)

    \(\Rightarrow\orbr{\begin{cases}x^2=4^2\\x^2=\left(-4\right)^2\end{cases}\Rightarrow}\orbr{\begin{cases}x=4\\x=-4\end{cases}}\)

    Vậy x = 4 hoặc x = -4

    2) \(\frac{-5}{x}=\frac{20}{28}\)

    \(\Rightarrow\frac{-5}{x}=\frac{5}{7}\)

    \(\Rightarrow5\times x=\left(-5\right)\times7\)

    \(\Rightarrow5\times x=-35\)

    \(\Rightarrow x=\left(-35\right):5\)

    \(\Rightarrow x=-7\)

    Vậy x = -7

    3) \(\frac{x}{2}-\frac{11}{5}=\frac{7}{8}\times\frac{64}{49}\)

    \(\Rightarrow\frac{x}{2}-\frac{11}{5}=\frac{8}{7}\)

    \(\Rightarrow\frac{x}{2}=\frac{8}{7}+\frac{11}{5}\)

    \(\Rightarrow\frac{x}{2}=\frac{117}{35}\)

    \(\Rightarrow35x=117\times2\)

    \(\Rightarrow35x=234\)

    \(\Rightarrow x=234:35\)

    \(\Rightarrow x=\frac{234}{35}\)

    Vậy  \(x=\frac{234}{35}\)

    4) \(\frac{x}{5}+\frac{9}{2}=\frac{6}{7}\times\frac{36}{48}\)

    \(\Rightarrow\frac{x}{5}+\frac{9}{2}=\frac{9}{14}\)

    \(\Rightarrow\frac{x}{5}=\frac{9}{14}-\frac{9}{2}\)

    \(\Rightarrow\frac{x}{5}=\frac{-27}{7}\)

    \(\Rightarrow7x=\left(-27\right)\times5\)

    \(\Rightarrow7x=-135\)

    \(\Rightarrow x=\left(-135\right):7\)

    \(\Rightarrow x=\frac{-135}{7}\)

    Vậy  \(x=\frac{-135}{7}\)

    5) \(\frac{3}{x-5}=\frac{-4}{x+2}\)

    \(\Rightarrow\frac{3}{x-5}+\frac{4}{x+2}=0\)

    \(\Rightarrow3\left(x+2\right)+4\left(x-5\right)=0\)

    \(\Rightarrow3x+6+4x-20=0\)

    \(\Rightarrow\left(3x+4x\right)+\left(6-20\right)=0\)

    \(\Rightarrow7x-14=0\)

    \(\Rightarrow7x=14\)

    \(\Rightarrow x=14:7\)

    \(\Rightarrow x=2\)

    Vậy x = 2

    _Chúc bạn học tốt_

    31 tháng 1 2019

    zài thế

    18 tháng 4 2018

    Bài 1 : 

    \(4\left(x-1\right)^{100}-3^{100}=3^{101}\)

    \(\Leftrightarrow\)\(4\left(x-1\right)^{100}=3^{101}+3^{100}\)

    \(\Leftrightarrow\)\(4\left(x-1\right)^{100}=3^{100}\left(3+1\right)\)

    \(\Leftrightarrow\)\(4\left(x-1\right)^{100}=3^{100}.4\)

    \(\Leftrightarrow\)\(\left(x-1\right)^{100}=3^{100}\)

    \(\Leftrightarrow\)\(\orbr{\begin{cases}\left(x-1\right)^{100}=3^{100}\\\left(x-1\right)^{100}=\left(-3\right)^{100}\end{cases}\Leftrightarrow\orbr{\begin{cases}x-1=3\\x-1=-3\end{cases}}}\)

    \(\Leftrightarrow\)\(\orbr{\begin{cases}x=3+1\\x=-3+1\end{cases}\Leftrightarrow\orbr{\begin{cases}x=4\\x=-2\end{cases}}}\)

    Vậy \(x=-2\) hoặc \(x=4\)

    Chúc bạn học tốt ~ 

    ai giúp mk bài 2 với

    10 tháng 8 2016

    Toán lớp 6

    10 tháng 8 2016

    1) \(\frac{2}{3}+x=-\frac{4}{5}\)

    \(x=\left(-\frac{4}{5}\right)-\frac{2}{3}\)

    \(x=-1\frac{7}{15}\)

    Vậy \(x=-1\frac{7}{15}\)

    2) \(\frac{2}{5}-x=-\frac{1}{3}\)

    \(x=\frac{2}{5}-\left(-\frac{1}{3}\right)\)

    \(x=\frac{11}{15}\)

    Vậy \(x=\frac{11}{15}\)

    3) \(1-\frac{x}{3}=1\frac{1}{2}\)

    \(\frac{x}{3}=1-1\frac{1}{2}\)

    \(\frac{x}{3}=-\frac{1}{2}\)

    \(\Rightarrow x=\frac{\left(-1\right)\cdot3}{2}\)

    \(x=-1\frac{1}{2}\)

    4) \(1-\left(\frac{2x}{3}+2\right)=-1\)

    \(\frac{2x}{3}+2=1-\left(-1\right)\)

    \(\frac{2x}{3}+2=2\)

    \(\frac{2x}{3}=2-2\)

    \(\frac{2x}{3}=0\)

    \(\Rightarrow x=0\)

    Vậy \(x=0\)

    11 tháng 8 2016

    1. \(\frac{25}{100}x+x-\frac{1}{5}x=\frac{1}{5}\)

    \(\Leftrightarrow\frac{1}{4}x+x-\frac{1}{5}x=\frac{1}{5}\)

    \(\Leftrightarrow\left(\frac{1}{4}+1-\frac{1}{5}\right)x=\frac{1}{5}\)

    \(\Leftrightarrow\frac{21}{20}x=\frac{1}{5}\)

    \(\Leftrightarrow x=\frac{1}{5}:\frac{21}{20}\)

    \(\Leftrightarrow x=\frac{4}{21}\)

     

    11 tháng 8 2016

    Chút nữa tớ làm cho

    10 tháng 3 2020

    2) Ta có: \(\left(2x+1\right).\left(3y-2\right)=-55=\left(-1\right).55=1.\left(-55\right)=\left(-5\right).11=5.\left(-11\right)\)

    - Ta có bảng giá trị: 

    \(2x+1\)\(-55\)\(-11\)\(-5\) \(-1\)\(1\)      \(5\)     \(11\)   \(55\)  
    \(3y-2\)\(1\)\(5\)\(11\)\(55\)\(-55\)\(-11\)\(-5\)\(-1\)
    \(x\)\(-28\)\(-6\)\(-3\)\(-1\)\(0\)\(2\)\(5\)\(27\)
    \(y\)\(1\)\(\frac{7}{3}\)\(\frac{13}{3}\)\(19\)\(-\frac{53}{3}\)\(-3\)\(-1\)\(\frac{1}{3}\)
     \(\left(TM\right)\)\(\left(L\right)\)\(\left(L\right)\)\(\left(TM\right)\)\(\left(L\right)\)\(\left(TM\right)\)\(\left(TM\right)\)\(\left(L\right)\)

    Vậy \(\left(x,y\right)\in\left\{\left(-28,1\right);\left(-1,19\right);\left(2,-3\right);\left(5,-1\right)\right\}\)

    3) Ta có: \(\left(x-2\right).\left(y+3\right)=5=\left(-1\right).\left(-5\right)=1.5\)

    - Ta có bảng giá trị:

    \(x-2\)\(-1\)\(1\)   \(-5\)\(5\)   
    \(y+3\)\(-5\)\(5\)\(-1\)\(1\)
    \(x\)\(1\)\(3\)\(-3\)\(7\)
    \(y\)\(-8\)\(2\)\(-4\)\(-2\)
     \(\left(TM\right)\)\(\left(TM\right)\)\(\left(TM\right)\)\(\left(TM\right)\)

    Vậy \(\left(x,y\right)\in\left\{\left(1,-8\right);\left(3,2\right);\left(-3,-4\right);\left(7,-2\right)\right\}\)

    4) Ta có: \(\left(2x+3\right).\left(y-5\right)=10=\left(-1\right).\left(-10\right)=1.10=\left(-2\right).\left(-5\right)=2.5\)

    - Vì \(x\in Z\)mà \(2x+3\)là số lẻ \(\Rightarrow\)\(2x+3\in\left\{-1,1,-5,5\right\}\)

    - Ta có bảng giá trị:

    \(2x+3\)\(-1\)  \(1\)     \(-5\) \(5\)     
    \(y-5\)\(-10\)\(11\)\(-2\)\(2\)
    \(x\)\(-2\)\(-1\)\(-4\)\(1\)
    \(y\)\(-5\)\(16\)\(3\)\(7\)
     \(\left(TM\right)\)\(\left(TM\right)\)\(\left(TM\right)\)\(\left(TM\right)\)

    Vậy \(\left(x,y\right)\in\left\{\left(-2,-5\right);\left(-1,16\right);\left(-4,3\right);\left(1,7\right)\right\}\)