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

Toán Lớp 8: a) $x^{2}$ + 4x – $y^{2}$ + 4 b) $x^{2}$ – 4 – 2xy + $y^{2}$ c) $4x^{2}$ – 4x – 3

Toán Lớp 8: a) $x^{2}$ + 4x – $y^{2}$ + 4
b) $x^{2}$ – 4 – 2xy + $y^{2}$
c) $4x^{2}$ – 4x – 3

Comments ( 2 )

  1. a) x^2 + 4x – y^2 + 4
    = ( x^2 + 2 . x . 2+ 2^2 ) – y^2
    = ( x + 2 )^2 – y^2
    = ( x + 2 + y ) ( x + 2 – y )
    b) x^2 – 4 – 2xy + y^2
    = ( x^2 – 2xy + y^2 ) – 2^2
    = ( x – y )^2 – 2^2
    = ( x – y + 2 ) ( x – y – 2 )
    c) 4x^2 – 4x – 3
    = 4x^2 + 2x – 6x – 3
    = 2x ( 2x + 1 ) – 3 ( 2x + 1 )
    = ( 2x + 1 ) ( 2x – 3 )

  2. Giải đáp:
     
    CHO MÌNH HAY NHẤT NHA
     

    toan-lop-8-a-2-4-y-2-4-b-2-4-2y-y-2-c-4-2-4-3

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