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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: Tim xy € Z a,3x + 4y – x y = 16 b,xy-3x=-19

Home/ Toán Lớp 8: Tim xy € Z a,3x + 4y – x y = 16 b,xy-3x=-19

Toán Lớp 8: Tim xy € Z a,3x + 4y – x y = 16 b,xy-3x=-19

Tháng Một 30, 2023 Toán học 2 Comments 0 views

Toán Lớp 8: Tim xy € Z
a,3x + 4y – x y = 16
b,xy-3x=-19

Comments ( 2 )

  1. quynhthanhnhu
    quynhthanhnhu
    30 Tháng Một, 2023 at 9:45 sáng
    Reply
    Giải đáp:
     
    Lời giải và giải thích chi tiết:
    3x+4y−xy=16⇔3x+4y−xy−12=16−12⇔(3x−xy)−(12−4y)=4⇔x(3−y)−4(3−y)=4⇔(3−y)(x−4)=4
    =>(3-y)(x-4) = 1*4=-1*-4=-4*-1=-1*-4=2*2=-2*-2
    =>(3-y)(x-4) = 1*4 =>y=2;x=8
    =>(3-y)(x-4) = -1*-4=>y=4; x=0
    =>(3-y)(x-4) = 2*2=> x=6;y=1
    =>(3-y)(x-4) =-2*-2=>x=2;y=5
    ;
    x(y-3)=-19
    x(y-3)=1*-19=-1*19 =19*1=-19*-1
    TH 1: x=1;y-3=-19 =>y=-16
    TH 2: x=-1;y-3= 19 =>y=22
    Tương tự
    (x,y)=(-19;4);(19;2);(-1;22);(1;-16)

  2. chauhoangmy98
    chauhoangmy98
    30 Tháng Một, 2023 at 9:44 sáng
    Reply
    a,3x + 4y – x y = 16
    ⇔ 3x + 4y – xy  – 12 = 16 -12
    ⇔ (3x – xy) – (12-4y)=4
    ⇔ x(3-y) – 4(3-y) = 4
    ⇔ (3-y)(x-4) = 4
    $\left \{ {{3-y=2} \atop {x-4=2}} \right.$
    ⇔ $\left \{ {{y=1} \atop {x=6}} \right.$
    $\left \{ {{3-y=-2} \atop {x-4=-2}} \right.$
    ⇔ $\left \{ {{y=5} \atop {x=2}} \right.$
    $\left \{ {{3-y=1} \atop {x-4=4}} \right.$
    ⇔ $\left \{ {{y=2} \atop {x=8}} \right.$
    $\left \{ {{3-y=-1} \atop {x-4=-4}} \right.$
    ⇔ $\left \{ {{y=4} \atop {x=0}} \right.$
    $\left \{ {{3-y=4} \atop {x-4=1}} \right.$
    ⇔ $\left \{ {{y=-1} \atop {x=5}} \right.$
    $\left \{ {{3-y=-4} \atop {x-4=-1}} \right.$
    ⇔ $\left \{ {{y=7} \atop {x=3}} \right.$
    ⇒ (y;x)∈{(2;8);(7;3);(4;0);(-1;5);(1;6);(5;2)}
    b)xy – 3x=-19
    ⇔x(y-3)=-19=-1.19=-19.1
    $\left \{ {{x=1} \atop {y-3=-19}} \right.$
    ⇔ $\left \{ {{x=1} \atop {y=-16}} \right.$
    $\left \{ {{x=-19} \atop {y-3=1}} \right.$
    ⇔ $\left \{ {{x=-19} \atop {y=4}} \right.$
    $\left \{ {{x=-1} \atop {y-3=19}} \right.$
    ⇔ $\left \{ {{x=-1} \atop {y=22}} \right.$
    $\left \{ {{x=19} \atop {y-3=-1}} \right.$
    ⇔ $\left \{ {{x=19} \atop {y=2}} \right.$
    ⇒(x,y)∈{(-19;4);(19;2);(-1;22);(1;-16)}
     
     

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222-9+11+12:2*14+14 = ? ( )

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