Tìm x,y biết: { x + y = 5 { 5x + 2y = 19

Question

Tìm x,y biết:
{ x + y = 5
{ 5x + 2y = 19

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Madeline 1 năm 2021-09-25T14:45:44+00:00 2 Answers 9 views 0

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  1. aihong
    0
    2021-09-25T14:46:50+00:00
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    Em xem hình 

  2. quynhnghi
    0
    2021-09-25T14:46:50+00:00
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    $\text { Đáp án: }$

    $\left \{ {{x+y=5} \atop {5x+2y=19}} \right.$

    ` <=> ` $\left \{ {{y=5-x} \atop {5x+2y=19}} \right.$ 

    ` <=> ` $\left \{ {{y=5-x} \atop {5x+2(5-x)=19}} \right.$ 

    ` <=> ` $\left \{ {{y=5-x} \atop {5x+10-2x=19}} \right.$ 

    ` <=> ` $\left \{ {{y=5-x} \atop {5x-2x=19-10}} \right.$ 

    ` <=> ` $\left \{ {{y=5-x} \atop {3x=9}} \right.$ 

    ` <=> ` $\left \{ {{y=5-x} \atop {x=3}} \right.$ 

    ` <=> ` $\left \{ {{y=5-3} \atop {x=3}} \right.$ 

    ` <=> ` $\left \{ {{y=2} \atop {x=3}} \right.$ 

    $\text { Vậy }$ $\left \{ {{y=2} \atop {x=3}} \right.$ 

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