Giải cách hpt sau giúp mik vs mn

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Giải cách hpt sau giúp mik vs mn
giai-cach-hpt-sau-giup-mik-vs-mn

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Khoii Minh 5 years 2020-10-26T07:04:30+00:00 2 Answers 78 views 0

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  1. Delwyn
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    2020-10-26T07:05:34+00:00
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  2. Dulcie
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    2020-10-26T07:05:40+00:00
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    Đáp án: $a$) `(x;y)=(2;-1)`.

                 $b$) `(x;y)=(1;-5)`.

                 $c$) `(x;y)=(16/7;-19/7)`.

    Giải thích các bước giải:

    $a$) $\left\{\begin{matrix}4x+5y=3& \\x-3y=5&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}4x+5y=3& \\4x-12y=20&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}4x+5y-4x+12y=3-20=-17& \\4x-12y=20&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}17y=-17& \\x-3y=5&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}y=-1& \\x-3y=5&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}y=-1& \\x=2&\end{matrix}\right.$

       Vậy `(x;y)=(2;-1)`.

    $b$) $\left\{\begin{matrix}2x+y=-3& \\2x-3y=17&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}2x+y-2x+3y=-3-17=-20& \\2x-3y=17&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}4y=-20& \\2x-3y=17&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}y=-5& \\2x-3y=17&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}y=-5& \\x=1&\end{matrix}\right.$

       Vậy `(x;y)=(1;-5)`.

    $c$) $\left\{\begin{matrix}5x-5y=25& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}5.(x-y)=25& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}x-y=5& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}3x-3y=15& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}3x-3y-3x-4y=15-(-4)=19& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}-7y=19& \\3x+4y=-4&\end{matrix}\right.$

    $⇒$ $\left\{\begin{matrix}y=\dfrac{-19}{7}& \\x=\dfrac{16}{7}&\end{matrix}\right.$

       Vậy `(x;y)=(16/7;-19/7)`.

     

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