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

Toán Lớp 8: Phân tích đa thức thành nhân tử: x^3-7x-6

Toán Lớp 8: Phân tích đa thức thành nhân tử:
x^3-7x-6

Comments ( 2 )

  1. Giải đáp:
    x^3-7x-6
    = x^3+x^2-x^2-x-6x-6
    = x^2(x+1)-x(x+1)-6(x+1)
    = (x+1)(x^2-x-6)
    = (x+1)(x^2-3x+2x-6)
    = (x+1)[x(x-3)+2(x-3)]
    = (x+1)(x-3)(x+2)

  2. $x^{3}$ $-$ $7x$ $-$ $6$
    $=$ $x^{3}$ $+$ $3x^{2}$ $+$ $2x$ $-$ $3x^{2}$ $-$ $9x$ $-$ $6$
    $=$ $x.(x^{2}$ $+$ $3x$ $+$ $2$$)$ $-$ $3.(x^{2}$ $+$ $3x$ $+$ $2$$)$
    $=$ $(x-3)$.$(x^{2}$ $+$ $3x$ $+$ $2$$)$
    $=$ $(x-3)$.$(x^{2}$ $+$ $2x$ $+$ $x$ $+$ $1$ $+$ $1$$)$
    $=$ $(x-3)$.$(x^{2}$ $+$ $2x$ $+$ $1$ $+$ $1$ $+$ $x$$)$
    $=$ $(x-3)$.$[$$(x+1)^{2}$ $+$ $(x+1)$$]$
    $=$ $(x-3)$.$(x+1)$.$(x+2)$

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

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