Phân tích đa thức thành nhân tử: a,3x^3+12x^2+12x b, 4x^2+4x-9x^2+1 c, x^2+4x-2xy-4y+y^2 02/12/2021 Bởi Mackenzie Phân tích đa thức thành nhân tử: a,3x^3+12x^2+12x b, 4x^2+4x-9x^2+1 c, x^2+4x-2xy-4y+y^2
`a)3x^3+12x^2+12x` `=3x(x^2+4x+4)` `=3x(x+2)^2` `b)4x^2+4x-9x^2+1` `=(4x^2+4x+1)-9x^2` `=[(2x)^2+2.2x.1+1^2]-(3x)^2` `=(2x+1)^2-(3x)^2` `=(2x+1-3x)(2x+1+3x)` `=(-x+1)(5x+1)` `c)x^2+4x-2xy-4y+y^2` `=(x^2-2xy+y^2)+(4x-4y)` `=(x-y)^2-4(x-y)` `=(x-y)(x-y-4)` Bình luận
`a)3x^3+12x^2+12x`
`=3x(x^2+4x+4)`
`=3x(x+2)^2`
`b)4x^2+4x-9x^2+1`
`=(4x^2+4x+1)-9x^2`
`=[(2x)^2+2.2x.1+1^2]-(3x)^2`
`=(2x+1)^2-(3x)^2`
`=(2x+1-3x)(2x+1+3x)`
`=(-x+1)(5x+1)`
`c)x^2+4x-2xy-4y+y^2`
`=(x^2-2xy+y^2)+(4x-4y)`
`=(x-y)^2-4(x-y)`
`=(x-y)(x-y-4)`