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

Toán Lớp 9: Giá trị của biểu thức A = x(2x + 3) – 4(x + 1) – 2x(x – 1/2) là?

Toán Lớp 9: Giá trị của biểu thức A = x(2x + 3) – 4(x + 1) – 2x(x – 1/2) là?

Comments ( 2 )

  1. Answer
    A = x . (2x + 3) – 4 . (x + 1) – 2x . (x – 1/2)
    A = x . 2x + x . 3 – 4 . x – 4 . 1 – 2x . x + 2x . 1/2
    A = 2x^2 + 3x – 4x – 4 – 2x^2 + x
    A = (2x^2 – 2x^2) + (3x – 4x + x) – 4
    A = (-x + x) – 4
    A = -4

  2. $A=x\left(2x+3\right)-4\left(x+1\right)-2x\left(\frac{x-1}{2}\right)$
    $=x\left(2x+3\right)-4\left(x+1\right)-2x\frac{x-1}{2}$
    $=x\left(2x+3\right)-4\left(x+1\right)-x\left(x-1\right)$
    $=2x^2+3x-4\left(x+1\right)-x\left(x-1\right)$
    $=2x^2+3x-4x-4-x\left(x-1\right)$
    $=2x^2+3x-4x-4-x^2+x$
    $=2x^2-x^2+3x-4x+x-4$
    $=x^2+3x-4x+x-4$
    $=x^2-4$
     

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

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