x^4+3x^2-9x-27 x^4+3x^3-9x-9 x^3-3x^2+3x-1-8y^3

0 bình luận về “x^4+3x^2-9x-27 x^4+3x^3-9x-9 x^3-3x^2+3x-1-8y^3”

1. Sửa đề:`x^4+3x^2-9x-27→x^4+3x^3-9x-27`

   `+)` 

    `x^4+3x^3-9x-27`

   `=(x^4+3x^3)-(9x+27)`

   `=x^3(x+3)-9(x+3)`

   `=(x+3)(x^3-9)`

   `+)`

   `x^4+3x^3-9x-9`

   `=(x^4-9)+(3x^3-9x)`

   `=[(x^2)^2-3^2]+3x(x^2-3)`

   `=(x^2-3)(x^2+3)+3x(x^2-3)`

   `=(x^2-3)(x^2+3x+3)`

   `+)`

   `x^3-3x^2+3x-1-8y^3`

   `=(x^3-3x^2+3x-1)-8y^3`

   `=(x-1)^3-(2y)^3`

   `=(x-1-2y)[(x-1)^2+(x-1).2y+(2y)^2]`

   `=(x-2y-1)(x^2-2x+1+2xy-2y+4y^2)`

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