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

Toán Lớp 8: x^4+27x x^3-x^2y-4x+4y x^2-8x+15

Toán Lớp 8: x^4+27x
x^3-x^2y-4x+4y
x^2-8x+15

Comments ( 2 )

  1. x^4+27x=x(x^3+27)$\\$x^3-x^2y-4x+4y=x^2(x-y)-4(x-y)=(x^2-4)(x-y)=(x-2)(x+2)(x-y)$\\$x^2-8x+15=x^2-3x-5x+15=x(x-3)-5(x-3)=(x-3)(x-5)
     

  2. Giải đáp:
    1)x(x+3)(x^2-3x+9)
    2)(x-y)(x+2)(x-2)
    3)(x-3)(x-5)
    Lời giải và giải thích chi tiết:
    1)x^4+27x
    =x(x^3+27)
    =x(x^3+3^3)
    =x(x+3)(x^2-x.3+3^2)
    =x(x+3)(x^2-3x+9)
    2)x^3-x^2y-4x+4y
    =(x^3-x^2y)-(4x-4y)
    =x^2(x-y)-4(x-y)
    =(x-y)(x^2-4)
    =(x-y)(x^2-2^2)
    =(x-y)(x+2)(x-2)
    3)x^2-8x+15
    =x^2-3x-5x+15
    =(x^2-3x)-(5x-15)
    =x(x-3)-5(x-3)
    =(x-3)(x-5)

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