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

Toán Lớp 8: a) 8xm^3-8xm^4 b) X^2-9x+9y-y^2 c)3x^3-9+x^2-27xy d) 8x^2-18xy+7y^2 = 8x^2 -14xy-4xy+7y^2

Toán Lớp 8: a) 8xm^3-8xm^4
b) X^2-9x+9y-y^2
c)3x^3-9+x^2-27xy
d) 8x^2-18xy+7y^2 = 8x^2 -14xy-4xy+7y^2

Comments ( 2 )

  1. Lời giải và giải thích chi tiết:
    a) 8xm^3-8xm^4
    = 8xm[m^2-(n^2)^2]
    = 8xm(m-n^2)(m+n^2)
    b) x^2-9x+9y-y^2
    = (x^2 – y^2)+(-9x+9y)
    = (x-y)(x+y) – 9(x-y)
    = (x-y)(x+y-9)
    c) 3x^3-9+x^2-27xy
    = (3x^3y-27xy)+(x^2-3^2)
    = 3xy(x^2-3^2)+(x^2-3^2)
    = (x^2-3^2)(3xy+1) = (x-3)(x+3)(3xy+1)
    d) 8x^2-18xy+7y^2
    = 8x^2 -14xy-4xy+7y^2
    = (8x^2-4xy)+(-14xy+7y^2)
    = 4x(2x-y)-7y(2x-y)
    = (4x-7y)(2x-y)

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

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