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

Toán Lớp 8: 1) x^2 – 3x + xy – 3y thành phân tử là ? 2) (7xy^2 – 14x^2y) : 7x 3) đa thức 2x^2 + 4x – 6 giúp mình với

Toán Lớp 8: 1) x^2 – 3x + xy – 3y thành phân tử là ?
2) (7xy^2 – 14x^2y) : 7x
3) đa thức 2x^2 + 4x – 6
giúp mình với

Comments ( 2 )

  1. 1) x^2 – 3x + xy – 3y
    =(x^2-3x)+(xy-3y)
    =x(x-3)+y(x-3)
    =(x-3)(x+y)
    2) (7xy^2 – 14x^2y) : 7x
    =7xy^2: 7x-14x^2y: 7x
    =y^2-2xy
    3) 2x^2 + 4x – 6
    =2(x^2+2x-3)
    =2(x^2+2x+1-4)
    =2[(x^2+2x+1)-4]
    =2[(x+1)^2-2^2]
    =2(x+1+2)(x+1-2)
    =2(x+3)(x-1)

  2. 1,
    x^2-3x+xy-3y
    =(x^2+xy)-(3x+3y)
    =x(x+y)-3(x+y)
    =(x+y)(x-3)
    2,
    (7xy^2-14x^2y): 7x
    =7xy^2: 7x- 14x^2y: 7x
    =y^2-2xy
    =y(y-2x)
    3,
    2x^2+4x-6
    =2x^2-2x+6x-6
    =2x(x-1)+6(x-1)
    =(x-1)(2x+6)
    =2.(x-1)(x+3)
     

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