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

Toán Lớp 8: thực hiện phép nhân a. (2x-1).x+x^2-2(x-3) b. x(2xx^2-3x)-(x+1)(x^2-2) c. 3x(x-1)+x^2(x-2)+3(x-1)(x+1)

Toán Lớp 8: thực hiện phép nhân
a. (2x-1).x+x^2-2(x-3)
b. x(2xx^2-3x)-(x+1)(x^2-2)
c. 3x(x-1)+x^2(x-2)+3(x-1)(x+1)

Comments ( 2 )

  1. a) (2x-1)x+x^2-2(x-3)
    =2x^2-x+x^2-2x+6
    =3x^2-3x+6
    b) x(2x^2-3x)-(x+1)(x^2-2)
    =2x^3-3x^2-(x^3-2x+x^2-2)
    =2x^3-3x^2-x^3-x^2+2x+2
    =x^3-4x^2+2x+2
    c) 3x(x-1)+x^2(x-2)+3(x-1)(x+1)
    =3x^2-3x+x^3-2x^2+3(x^2-1)
    =x^3+x^2-3x+3x^2-3
    =x^3+4x^2-3x-3

  2. a)
    (2x-1)x+x^2-2(x-3)
    =2x^2-x+x^2-2x+6
    =(2x^2+x^2)-(x+2x)+6
    =3x^2-3x+6
    b)
    x(2x^2-3x)-(x+1)(x^2-2)
    =2x^3-3x^2-(x^3-2x+x^2-2)
    =2x^3-3x^2-x^3-x^2+2x+2
    =(2x^3-x^3)-(3x^2+x^2)+2x+2
    =x^3-4x^2+2x+2
    c)
    3x(x-1)+x^2(x-2)+3(x-1)(x+1)
    =3x^2-3x+x^3-2x^2+3(x^2-1)
    =x^3+3x^2-2x^3-3x+3x^2-3
    =x^3+(3x^2-2x^3+3x^2)-3x-3
    =x^3+4x^2-3x-3

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

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