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

Toán Lớp 8: tính::::::::::::::::::::::::::::::::::::: (x+y)^2-3^2=

Toán Lớp 8: tính:::::::::::::::::::::::::::::::::::::
(x+y)^2-3^2=

Comments ( 2 )

  1. (x+y)^2-3^2
    =(x+y-3)(x+y+3)
    @ Áp dụng hằng đẳng thức số 3 : A^2-B^2=(A-B)(A+B)
     

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

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