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

Toán Lớp 8: a. x^2+4xy-4x^2+4y^2 b. x^2+2x-15

Toán Lớp 8: a. x^2+4xy-4x^2+4y^2
b. x^2+2x-15

Comments ( 2 )

  1. a, x^2 + 4xy – 4x^2 + 4y^2
    = ( x^2 + 4xy + 4y^2 ) – 4x^2
    = ( x+ 2y)^2 – (2x)^2
    = ( x+ 2y + 2x )( x + 2y – 2x)
    = ( 2y + 3x)( 2x – x)
    b, x^2 + 2x -15
    = x^2 + 3x – 5x -15
    = x( x + 3) – 5( x+3)
    = (x+3)(x-5)
     

  2. $@Shu$
    a) x^2 + 4xy – 4x^2 + 4y^2
    ⇔[x^2 + 2x2y – (2y)^2] – (2x)^2
    ⇔(x – 2y)^2 – (2x)^2
    ⇔(x-2y – 2x ) (x – 2y +2x) 
    ⇔(-x – 2y)(3x – 2y)
    b) x^2 + 2x -15
    ⇔x^2 + 2x + 1 – 16
    ⇔(x^2 + 2x +1) – 4^2
    ⇔(x+1)^2 – 4^2
    ⇔(x+1-4)(x+1 +4)
    ⇔(x -3)(x+5)

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

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