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

Toán Lớp 8: a) (xy-1) ^2 – ( xy -1 ) ( xy + 2)

Toán Lớp 8: a) (xy-1) ^2 – ( xy -1 ) ( xy + 2)

Comments ( 2 )

  1. a)(xy-1)^2-(xy-1)(xy+2)
    =(xy-1)[(xy-1)-(xy+2)]
    =(xy-1)(xy-1-xy-2)
    =-3(xy-1)
    =-3xy+3

  2. (xy-1)^2-(xy-1)(xy+2)
    =(xy-1)[(xy-1)-(xy+2)]
    =(xy-1)(xy-1-xy-2) do đằng trước ngoặc là dấu trừ nên khi bỏ ngoặc là đổi dấu
    =-3(xy-1)
    =-3xy+3

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