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

Toán Lớp 8: 1) Viết dưới dạng tích: x3 – 27 2) Tính: (x – y)(x2 – xy + y2)

Toán Lớp 8: 1) Viết dưới dạng tích: x3 – 27
2) Tính: (x – y)(x2 – xy + y2)

Comments ( 2 )

  1. x^3-27
    =x^3-3^3
    =(x-3)(x^2+3x+3^2)
    =(x-3)(x^2+3x+9)
    ———————————
    (x-y)(x^2-xy+y^2)
    =x^3-x^2y+xy^2-x^2y+xy^2-y^3
    =x^3-2x^2y+2xy^2-y^3

  2. 1)x^3-27=x^3-3^3 
    =(x-3)(x^2+3x+9)
    2)(x-y)(x^2-xy+y^2)
    =x^3-x^2y+xy^2-x^2y+xy^2-y^3
    =x^3-2x^2y+2xy^2-y^3
     

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