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

Toán Lớp 8: a)25x^2-9.(x+y)^2 b)x^2 +2x-15 c) 3x^2-11x+6

Toán Lớp 8: a)25x^2-9.(x+y)^2
b)x^2 +2x-15
c) 3x^2-11x+6

Comments ( 2 )

  1. a,
    25x^2-9(x+y)^2
    =(5x)^2-[3(x+y)]^2
    =(5x-3x-3y)(5x+3x+3y)
    =(2x-3y)(8x+3y)
    b,
    x^2+2x-15
    =x^2+5x-3x-15
    =x(x+5)-3(x+5)
    =(x+5)(x-3)
    c,
    3x^2-11x+6
    =3x^2-2x-9x+6
    =x(3x-2)-3(2x-2)
    =(3x-2)(x-3)

  2. a) 25x^2-9(x+y)^2
    =(5x)^2-[3(x+y)]^2
    =[5x-3(x+y)][5x+3(x+y)]
    =(5x-3x-3y)(5x+3x+3y)
    =(2x-3y)(8x+3y)
    * a^2-b^2=(a-b)(a+b)
    b) x^2+2x-15
    =(x^2-3x)+(5x-15)
    =x(x-3)+5(x-3)
    =(x-3)(x+5)
    * Tách hạng tử
    * Nhóm hạng tử
    * Đặt nhân tử chung
    c) 3x^2-11x+6
    =(3x^2-2x)-(9x-6)
    =x(3x-2)-3(3x-2)
    =(3x-2)(x-3)
    * Tách hạng tử
    * Nhóm hạng tử
    * Đặt nhân tử chung
     

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