Bài `2`
`a, 2x^3 -6x^2`
`= 2x^2(x- 3)`
`b, 9x^2 -1/16y^2`
`= (3x)^2 -(1/4y)^2`
`=(3x-1/4y)(3x+1/4y)`
`c, x^2y +5xy^2 +6y^3`
`= y ( x^2 + 5xy+6y^2)`
`d, 3x^3 +6x^2y`
`= 3x^2 (x+ 2y)`
`e, -9+6x-x^2`
`= -(x^2-6x+9)`
`=-(x-3)^2`
`f, 2x^2 +3xy -5y^2`
`= x(2x+ 3y- 5y)`
`g, x^2 +12x+36`
`= x^2 + 2.x.6+6^2`
`=(x+6)^2`
`h, x^2 +1-y^2+2x`
`=(x^2 +2x+1)-y^2`
`=(x+1)^2-y^2`
`=(x+1-y)(x+1+y)`
`i, 4x^2 +12x+9`
`=(2x)^2 + 2.2x.3+3^2`
`=(2x+3)^2`
`j, 25-x^2 +2xy-y^2`
`= -(x^2 +2xy -y^2 +25)`
`= -x^2 -2xy +y^2 -25`
`=-(x-y)^2 -25`
`=-(x-y-5)(x-y+5)`
`k,x^2-25`
`=x^2-5^2`
`=(x-5)(x+5)`
`l, 3x^3y-12x^2y^2+12xy^3`
`= 3xy( x^2 - 4xy + 4y^2)`
`= 2xy( x-2y)^2`







