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

Toán Lớp 8: phân tích đa thức thành nhân tử x ³-2x ²y +xy ² -9x x^7+x ²+1

Toán Lớp 8: phân tích đa thức thành nhân tử x ³-2x ²y +xy ² -9x
x^7+x ²+1

Comments ( 2 )

  1. x³-2x²y+xy²-9x
    =x(x²-2xy+y²-9)
    =x[(x-y)^2-3^2]
    =x(x-y-3)(x-y+3)
    …..
    x^7+x²+1
    =x^7-x+(x²+x+1)
    =x(x^6-1)+(x^2+x+1)
    =x(x^3-1)(x^3+1)+(x^2+x+1)
    =x(x^3+1)(x-1)(x^2+x+1)+(x^2+x+1)
    =(x^2+x+1)[x(x^3+1)(x-1)+1]
    =(x^2+x+1)[(x^4+x)(x-1)+1]
    =(x^2+x+1)(x^5-x^4+x^2-x+1)
     

  2. x^3 – 2x^2y + xy^2 – 9x
    = x (x^2 – 2xy + y^2 – 9)
    = x [ (x^2 – 2xy + y^2) – 9]
    = x [ (x-y)^2 – 3^2]
    = x (x-y-3)(x-y+3)
    x^7 + x^2 + 1
    = (x^7 – x^6 + x^4 – x^3 + x^2) + (x^6 – x^5 + x^3 – x^2 + x) + (x^5 -x^4 + x^2 – x +1)
    =  x^2 (x^5 -x^4 + x^2 – x +1) + x(x^5 -x^4 + x^2 – x +1) + (x^5 -x^4 + x^2 – x +1)
    = (x^2 + x +1)(x^5 -x^4 + x^2 – x +1)
     

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

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