phân tích đa thức thành nhân tử x^2-49x x^5-4x^4+4x^3 2xy-x^2-y^2+81 5x5y+40x^2y giúp mình nha 01/07/2021 Bởi Rose phân tích đa thức thành nhân tử x^2-49x x^5-4x^4+4x^3 2xy-x^2-y^2+81 5x5y+40x^2y giúp mình nha
`a)x^2-49x.` `=x.(x-49).` `b)x^5-4x^4+4x^3.` `=x^3.(x^2-4x+4).` `=x^3.(x^2-2.x.2+2^2).` `=x^3.(x-2)^2.` `=x^3.(x-2).(x-2).` `c)2xy-x^2-y^2+81.` `=(-x^2+2xy-y^2)+81.` `=-(x^2-2xy+y^2)+81.` `=-(x-y)^2+81.` `=-(x-y)^2+9^2.` `=9^2-(x-y)^2.` `=[9+(x-y)].[9-(x-y)].` `=(9+x-y).(9-x+y).` `d)5x^5y+40x^2y.` `=5x^2y.(x^3+8).` Bình luận
`a)x^2-49x.`
`=x.(x-49).`
`b)x^5-4x^4+4x^3.`
`=x^3.(x^2-4x+4).`
`=x^3.(x^2-2.x.2+2^2).`
`=x^3.(x-2)^2.`
`=x^3.(x-2).(x-2).`
`c)2xy-x^2-y^2+81.`
`=(-x^2+2xy-y^2)+81.`
`=-(x^2-2xy+y^2)+81.`
`=-(x-y)^2+81.`
`=-(x-y)^2+9^2.`
`=9^2-(x-y)^2.`
`=[9+(x-y)].[9-(x-y)].`
`=(9+x-y).(9-x+y).`
`d)5x^5y+40x^2y.`
`=5x^2y.(x^3+8).`