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

Toán Lớp 6: Bài 2: Tìm x, biết a, -2.(x-3)-13=-15 b, 5-2.(x+1)=3^2+15 Giúp mình bài này với nha

Toán Lớp 6: Bài 2: Tìm x, biết
a, -2.(x-3)-13=-15
b, 5-2.(x+1)=3^2+15
Giúp mình bài này với nha

Comments ( 2 )

  1. a) -2. ( x – 3 ) – 13 = -15
    $\Rightarrow$ -2. ( x – 3 ) = -15 + 13
    $\Rightarrow$ -2. ( x – 3 ) = -2
    $\Rightarrow$ x – 3 = ( -2 ) : ( -2 )
    $\Rightarrow$ x – 3 = 1
    $\Rightarrow$ x = 1 + 3
    $\Rightarrow$ x = 4
              Vậy x = 4
    b) 5 – 2. ( x + 1 ) = $3^2$ + 15
    $\Rightarrow$ 5 – 2. ( x + 1 ) = 9  + 15
    $\Rightarrow$ 5 – 2. ( x + 1 ) = 24
    $\Rightarrow$ 2. ( x + 1 ) = 5 – 24
    $\Rightarrow$ 2. ( x + 1 ) = -19
    $\Rightarrow$ x + 1 = $\dfrac{-19}{2}$
    $\Rightarrow$ x = $\dfrac{-19}{2}$ – 1
    $\Rightarrow$ x = $\dfrac{-21}{2}$
                       Vậy x = $\dfrac{-21}{2}$

  2. Lời giải và giải thích chi tiết:
    Bài 2.
    a)
    -2.(x-3)-13=-15
    =>-2.(x-3)=-15+13
    =>-2.(x-3)=-2
    =>x-3=(-2):(-2)
    =>x-3=1
    =>x=1+3
    =>x=4
    Vậy x=4
    b)
    5-2.(x+1)=3^2+15
    =>5-2.(x+1)=9+15
    =>5-2.(x+1)=24
    =>2.(x+1)=5-24
    =>2.(x+1)=-19
    =>x+1=-19/2
    =>x=-19/2-1
    =>x=-19/2-2/2
    =>x=-21/2
    Vậy x=-21/2

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