Toán x^4+3x^2-9x-27 x^4+3x^3-9x-9 x^3-3x^2+3x-1-8y^3 11/07/2021 By Katherine x^4+3x^2-9x-27 x^4+3x^3-9x-9 x^3-3x^2+3x-1-8y^3
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)` Trả lời
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)`