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

Toán Lớp 6: 2x/3 = 3y/4 và x+y = 34 tìm x,y

Toán Lớp 6: 2x/3 = 3y/4 và x+y = 34
tìm x,y

Comments ( 2 )

  1. Đặt (2x)/3 = (3y)/4=k

    =>{(2x=3k=>x=(3k)/2),(3y=4k=>y=(4k)/3):}$(*)$

    Thay $(*)$ vào x+y = 34,ta có:

    (3k)/2 + (4k)/3=34

    =>(9k)/6 + (8k)/6=34

    =>(17k)/6=34

    =>17k=34.6

    =>17k=204

    =>k=204:17=12

    Với k=12 thì: {(x=(3.12)/2=42/2=21),(y=(4.12)/3=48/3=16):}

    Vậy (x;y) là: (21;16)

  2. (2x)/3=(3y)/4=>x/(3/2)=y/(4/3)
    Áp dụng tc dãy ts bằng nhau ta có:
    x/(3/2)=y/(4/3)=(x+y)/(3/2+4/3)=34/(17/6)=12
    =>x/(3/2)=12=>x=18
          y/(4/3)=12=>y=16
    Vậy (x;y)=(18;16)

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