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

Toán Lớp 8: Rút gọn biểu thức ($x+1)^{3}$ + ($x-1)^{3}$ + $x^{3}$ -3x(x+1)(x-1)

Toán Lớp 8: Rút gọn biểu thức ($x+1)^{3}$ + ($x-1)^{3}$ + $x^{3}$ -3x(x+1)(x-1)

Comments ( 2 )

  1. $(x+1)^3+(x-1)^3+x^3-3x(x+1)(x-1)$
    $=(x^3+3x^2+3x+1)+(x^3-3x^2+3x-1)+x^3-3x(x^2-1)$
    $=x^3+3x^2+3x+1+x^3-3x^2+3x-1+x^3-3x^3+3x$
    $=(x^3+x^3+x^3-3x^3)+(3x^2-3x^2)+(3x+3x+3x)+(1-1)$
    $=9x$

  2. Giải đáp:
    9x
    Lời giải và giải thích chi tiết:
    (x+1)³+(x-1)³+x³-3x(x+1)(x-1)
    =x³+3.x².1+3.x.1²+1³+x³-3.x².1+3.x.1²-1³+x³-3x(x²-1²)
    =x³+3x²+3x+1+x³-3x²+3x-1+x³-3x(x²-1)
    =x³+3x²+3x+1+x³-3x²+3x-1+x³-3x³+3x
    =(x³+x³+x³-3x³)+(3x²-3x²)+(3x+3x+3x)+(1-1)
    =9x

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