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Lê Quốc Trần Anh Coordinator

03/08/2017 at 08:54
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Find \(x,y\in Z\):

\(\dfrac{x}{6}-\dfrac{2}{y}=\dfrac{1}{30}\)




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  • ...
    Dao Trong Luan 03/08/2017 at 11:54

    \(\Rightarrow\dfrac{x}{6}-\dfrac{1}{30}=\dfrac{2}{y}\)

    \(\Rightarrow\dfrac{5x}{30}-\dfrac{1}{30}=\dfrac{2}{y}\)

    \(\Rightarrow\dfrac{5x-1}{30}=\dfrac{2}{y}\)

    \(\Rightarrow y\left(5x-1\right)=60\)

    But \(5x-1\equiv4\left(mod5\right)\)

    \(\Rightarrow5x-1\in\left\{-6;-1;4\right\}\)

    If 5x - 1 = -6

    => 5x = -5 => x = -1

    And y = 60 : -6 = -10

    If 5x-1 = -1 

    => 5x = 0 => x = 0

    And y = 60 : -1 = -60

    If 5x-1 = 4 

    => 5x = 5 => x = 1

    And y = 60 : 4 = 15

    So \(\left(x,y\right)=\left(-1;-10\right);\left(0;-60\right);\left(1;15\right)\)

    Lê Quốc Trần Anh selected this answer.
  • ...
    baohong912006 04/08/2017 at 08:38

    ⇒x6−130=2y⇒x6−130=2y

    ⇒5x30−130=2y⇒5x30−130=2y

    ⇒5x−130=2y⇒5x−130=2y

    ⇒y(5x−1)=60⇒y(5x−1)=60

    But 5x−1≡4(mod5)5x−1≡4(mod5)

    ⇒5x−1∈{−6;−1;4}⇒5x−1∈{−6;−1;4}

    If 5x - 1 = -6

    => 5x = -5 => x = -1

    And y = 60 : -6 = -10

    If 5x-1 = -1 

    => 5x = 0 => x = 0

    And y = 60 : -1 = -60

    If 5x-1 = 4 

    => 5x = 5 => x = 1

    And y = 60 : 4 = 15

    So (x,y)=(−1;−10);(0;−60);(1;15


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