`a)16x^3y+0,25yz^3`
`=0,25y(64x^3+z^3)`
`=0,25(4x+z)(16x^2-4xz+z^2)`
`b)x^4-4x^3+4x^2`
`=x^2(x^2-4x+4)`
`=x^2(x-2)^2`
`c)2ab^2-a^2b-b^3`
`=-b(-2ab+a^2+b^2)`
`=-b(a-b)^2`
`d)a^3+a^2b-ab^2-b^3`
`=a^2(a+b)-b^2(a+b)`
`=(a+b)(a^2-b^2)`
`=(a+b)(a-b)(a+b)`
`=(a+b)^2(a-b)`
`e)x^3+x^2-4x-4`
`=x^2(x+1)-4(x+1)`
`=(x+1)(x^2-4)`
`=(x+1)(x-2)(x+2)`
`f)x^3-x^2-x+1`
`=x^2(x-1)-(x-1)`
`=(x-1)(x^2-1)`
`=(x-1)^2(x+1)`
`g)x^4+x^3+x^2-1`
`=x^3(x+1)+(x-1)(x+1)`
`=(x+1)(x^3+x-1)`
`h)x^2y^2+1-x^2-y^2`
`=x^2(y^2-1)+(1-y^2)`
`=x^2(y-1)(y+1)-(y-1)(y+1)`
`=(y-1)(y+1)(x^2-1)`
`=(y-1)(y+1)(x-1)(x+1)`
`i)x^4-x^2+2x-1`
`=x^4+x^3-x^2-x^3-x^2+x+x^2+x-1`
`=x^2(x^2+x-1)-x(x^2+x-1)+(x^2+x-1)`
`=(x^2-x+1)(x^2+x-1)`
`11)3a-3b+a^2-2ab+b^2`
`=3(a-b)+(a-b)^2`
`=(a-b)(3+a-b)`
`12)a^2+2ab+b^2-2a-2b+1`
`=(b+a-1)^2`(hằng đẳng thức đặc biệt)
`13)a^2-b^2-4a+4b`
`=(a-b)(a+b)-4(a-b)`
`=(a-b)(a+b-4)`
`14)a^3-b^3-3a+3b`
`=(a-b)(a^2+ab+b^2)-3(a-b)`
`=(a-b)(a^2+ab+b^2-3)`
`15)x^3+3x^2-3x-1`
`=(x-1)(x^2+x+1)+3x(x-1)`
`=(x-1)(x^2+x+1+3x)`
`=(x-1)(x^2+4x+1)`
`16)x^3-3x^2-3x+1`
`=(x+1)(x^2-x+1)-3x(x+1)`
`=(x+1)(x^2-x+1-3x)`
`=(x+1)(x^2-4x+1)`
`17)x^3-4x^2+4x-1`
`=(x-1)(x^2+x+1)-4x(x-1)`
`=(x-1)(x^2-3x+1)`
