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

Toán Lớp 8: Phân tích đa thức a) x^2+16y^2-8xy b) x^2-2x+2xy-2y+y^2 c) x^2-4x-21 Giúp mk nhanh với

Toán Lớp 8: Phân tích đa thức
a) x^2+16y^2-8xy
b) x^2-2x+2xy-2y+y^2
c) x^2-4x-21
Giúp mk nhanh với

Comments ( 2 )

  1. a, x^2 + 16y^2 – 8xy
    = x^2 – 2.x .4y + (4y)^2
    =( x- 4y)^2
    b, x^2 – 2x + 2xy – 2y +y^2
    =(x^2 + 2xy +y^2 ) + (-2x -2y)
    =(x+y)^2  -2(x+y)
    =(x+y)(x+y-2)
    c, x^2 -4x -21
    = x^2 – 7x + 3x -21
    =x(x-7) + 3(x-7)
    =(x-7)(x+3)
     

  2. a)x^2+16y^2-8xy
    =x^2-8xy+16y^2
    =(x-4y)^2
    b)x^2-2x+2xy-2y+y^2
    =(x^2+2xy+y^2)-(2x+2y)
    =(x+y)^2-2(x+y)
    =(x+y)(x+y-2)
    c)x^2-4x-21
    =x^2-7x+3x-21
    =x(x-7)+3(x-7)
    =(x-7)(x+3)
     

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

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