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

Toán Lớp 8: (x+y)^3-3xy(x+y)-x^3+y^3 (Giup em gap voi )

Toán Lớp 8: (x+y)^3-3xy(x+y)-x^3+y^3 (Giup em gap voi )

Comments ( 2 )

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

  2. (x+y)^3-3xy.(x+y)-x^3+y^3
    =(x^3+3x^2y+3xy^2+y^3)-3x^2y-3xy^2-x^3+y^3
    =x^3+3x^2y+3xy^2+y^3-3x^2y-3xy^2-x^3+y^3
    =(x^3-x^3)+(3x^2y-3x^2y)+(3xy^2-3xy^2)+(y^3+y^3)
    =2y^3
    $#chúc tus học tốt!!$
    #La
     

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

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