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

Toán Lớp 8: tìm x a) x(x-1)-x^2=5 b) x^3 – 6x^2 +9x-xy^2 c) (x+4) (x^2 -4x +16)-x(x^2-2)

Toán Lớp 8: tìm x
a) x(x-1)-x^2=5
b) x^3 – 6x^2 +9x-xy^2
c) (x+4) (x^2 -4x +16)-x(x^2-2)

Comments ( 1 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
     a) 
    x(x-1)-x^2=5
    <=> x^2+x+x^2=5
    <=>-x=5
    <=> x=-5
    Vậy x=-5
    b)
    x^3-6x^2+9x-xy^2
    =x(x^2-6x+9-y^2)
    =x[(x-3)^2-y^2]=0
    =x(x+y-3)(x-y-3)
    c)
    (x+4)(x^2-4x+16)-x(x^2-2)
    =x^3+4^3-x^3+2x
    =64+2x
    =2(x+32)

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

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