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

Toán Lớp 8: (x-y)(x⁴+x³y+x²y²+xy³+y⁴)=x⁵-y⁵ chừng minh 2 biểu thức bằng nhau

Toán Lớp 8: (x-y)(x⁴+x³y+x²y²+xy³+y⁴)=x⁵-y⁵
chừng minh 2 biểu thức bằng nhau

Comments ( 2 )

  1. (x – y)(x⁴ + x³y + x²y² + xy³ + y⁴)
    = x(x⁴+x³y+x²y²+xy³+y⁴) – y(x⁴ + x³y + x²y²+xy³ + y⁴)
    = x⁵ + x⁴y + x³y² + x²y³ + xy⁴ – yx⁴ – x³y² – x²y³ – xy⁴ – y⁵
    = (x⁵ – y⁵) + (x⁴y – yx⁴) + (x³y² – x³y²) + (x²y³ – x²y³) + (xy⁴ – xy⁴)
    = x⁵ – y⁵

  2. #tnvt
    (x-y)(x^4+x^3y+x^2y^2+xy^3+y^4)
    =(x-y)(x^4+x^3y+x^2y^2)+(xy^3+y^4)(x-y)
    =x^2(x-y)(x^2+xy+y^2)+x^2y^3-xy^4+y^4x-y^5
    =x^2(x^3-y^3)+x^2y^3-xy^4+xy^4-y^5
    =x^5-x^2y^3+x^2y^3-y^5
    =x^5-y^5
    ->Đpcm

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

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