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

Toán Lớp 8: C = (x − y + 1)^3 − (x − y − 1)^3 − 6(x^2 − 2xy + y^2) giúp em ạ hứa cho ctlhn và 5sao

Toán Lớp 8: C = (x − y + 1)^3 − (x − y − 1)^3 − 6(x^2 − 2xy + y^2)
giúp em ạ hứa cho ctlhn và 5sao

Comments ( 1 )

  1. C = (x – y + 1)^3 – (x – y – 1)^3 – 6(x^2 – 2xy + y^2)
    Đặt  x – y = a
    ⇒ C = (a + 1)^3 – (a – 1)^3 – 6a^2
    C = (a^3 + 3a^2 + 3a + 1) – (a^3 – 3a^2 + 3a – 1) – 6a^2
    C = a^3 + 3a^2 + 3a + 1 – a^3 + 3a^2 – 3a + 1 – 6a^2
    C = 2

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