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

Toán Lớp 8: (x-3)(x^2+ 6x+9) -x(x^2-9) = 0

Toán Lớp 8: (x-3)(x^2+ 6x+9) -x(x^2-9) = 0

Comments ( 1 )

  1. $ (x-3)(x^2+ 6x+9) -x(x^2-9) = 0 $
    ⇒x^3+6x^2+9x-3x^2-18x-27-x^3+9x=0
    ⇒3x^2-27=0
    ⇔3x^2=27 hay 3x^2=-27
    ⇔x^2=9   hay x^2=-9
    ⇔x=3       hay x=-3
    Vậy x∈{3;-3}
    #tcv  

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