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

Toán Lớp 7: tim x 1/2 . | 3/5 . x – 1/3 | + 1/4 = 5/2

Toán Lớp 7: tim x
1/2 . | 3/5 . x – 1/3 | + 1/4 = 5/2

Comments ( 2 )

  1. 1/2 . |3/5 . x – 1/3 | + 1/4 = 5/2
    $\Leftrightarrow$ 1/2 . |3/5 . x – 1/3 | = 5/2 – 1/4
    $\Leftrightarrow$ 1/2 . |3/5 . x – 1/3 | = 5/2 – 1/4
    $\Leftrightarrow$ 1/2 . |3/5 . x – 1/3 | = 9/4
    $\Leftrightarrow$ |3/5 . x – 1/3 | = 9/4 : 1/2
    $\Leftrightarrow$ |3/5 . x – 1/3 | = 9/2
    $\Leftrightarrow$ 3/5 . x – 1/3 = 9/2 $\text{hoặc}$ 3/5 . x – 1/3 = (-9)/2
    $\Leftrightarrow$ 3/5 . x = 9/2 + 1/3 $\text{hoặc}$ 3/5 . x  = (-9)/2 + 1/3
    $\Leftrightarrow$ 3/5 . x = 29/6 $\text{hoặc}$ 3/5 . x  = (-25)/6
    $\Leftrightarrow$ x = 29/6 : 3/5 $\text{hoặc}$ x= (-25)/6 : 3/5
    $\Leftrightarrow$ x = 145/18 $\text{hoặc}$ x= -125/18
    $\text{Vậy x}$ $\in$ {145/18 ; -125/18}
     

  2. 1/2.|3/5 .x -1/3| +1/4=5/2
    <=>1/2.|3/5 x-1/3|=5/2-1/4
    <=>|3/5 x-1/3|=9/4:1/2
    <=>|3/5 x-1/3|=18/4=9/2
    <=>3/5 x-1/3=9/2 hoặc 3/5 x-1/3=-9/2
    <=>3/5 x=9/2+1/3 hoặc 3/5 x=-9/2+1/3
    <=>x=29/6:3/5 hoặc x=-25/6:3/5
    <=>x=145/18 hoặc x=-125/18
    Vậy S={145/18;-125/18}

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