Question

Bài 2: Phân tích các đa thức sau thành nhân tử
a) x²(x - y) + 2x - 2y
b) (5x - 2y)(5x + 2y) + 4y - 1
c) x² (xy + 1) + 2y - x -3xy

Answer 1

` a) x^2(x-y)+2x-2y `

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

` = (x<sup>2</sup>+2)(x-y) `

 ` b) (5x-2y)(5x+2y)+4y-1 `

` = 25x<sup>2</sup>-4y<sup>2</sup>+4y-1 `

` = 25x<sup>2</sup>-(4y<sup>2</sup>-4y+1) `

` = 25x<sup>2</sup>-(2y-1)<sup>2</sup>`

` = (5x-2y+1)(5x+2y-1) `

 ` c) x<sup>2</sup>(xy+1)+2y-x-3xy `
`= x^3y + x^2+2y-x-3xy`
`= x^3y -xy +x^2-x + 2y-2xy`
`= xy.(x^2-1) + x.(x-1) + 2y.(1-x)`
`= xy.(x-1)(x+1) + x.(x-1) -2y.(x-1)`
`= (x-1).[xy.(x+1) + x-2y]`
`= (x-1).(x^2y+1+x-2y)`