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

Toán Lớp 7: Tìm `x:` `2.(x-3)^2+5=13` `|3/5`$\sqrt{x}$`-1/20|-3/4=1/5`

Toán Lớp 7: Tìm x:
2.(x-3)^2+5=13
|3/5$\sqrt{x}$-1/20|-3/4=1/5

Comments ( 2 )

  1. 2 . (x – 3)^2 + 5 = 13
    2 . (x – 3)^2 = 13 – 5
    2 . (x – 3)^2 = 8
    (x – 3)^2 = 8 : 2
    (x – 3)^2 = 4
    => (x – 3)^2 = (±2)^2
    => x – 3 in {2; -2}
    => x in {5; 1}
    _________________________
    |3/5 \sqrt{x} – 1/20| – 3/4 = 1/5
    |3/5 \sqrt{x} – 1/20| = 1/5 + 3/4
    |3/5 \sqrt{x} – 1/20| = 19/20
    -> 3/5 \sqrt{x} – 1/20 in {19/20; -19/20}
    -> 3/5 \sqrt{x} in {1; -9/10}
    -> \sqrt{x} in {5/3; -3/2}
    \sqrt{x} ≥ 0
    => \sqrt{x} = 5/3
    => x = 25/9
     

  2. 2.(x-3)^2+5=13
    =>2.(x-3)^2=13-5
    =>2.(x-3)^2=8
    =>(x-3)^2=8:2
    =>(x-3)^2=4
    =>(x-3)^2=(+-2)^2
    =>x-3=2   hoặc   x-3=-2
    =>x=2+3   hoặc   x=-2+3
    =>x=5   hoặc   x=1
    Vậy x=5 hoặc x=1
    $\\$
    |3/5sqrtx-1/20|-3/4=1/5
    =>|3/5sqrtx-1/20|=1/5+3/4
    =>|3/5sqrtx-1/20|=19/20
    =>3/5sqrtx-1/20=19/20   hoặc   3/5sqrtx-1/20=-19/20
    =>3/5sqrtx=19/20+1/20   hoặc   3/5sqrtx=-19/20+1/20
    =>3/5sqrtx=1   hoặc   3/5sqrtx=-9/10
    =>sqrtx=1:3/5   hoặc   sqrtx=-9/10:3/5
    =>sqrtx=5/3   hoặc   sqrtx=-3/2
    Vì sqrtx>=0
    sqrtx=5/3
    =>x=25/9
    Vậy x=25/9
     

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