`1, `
`27+b^3`
`=3^3+b^3`
`=(3+b)(9-3b+b^2)`
`2, `
`a^2 -64`
`=a^2-8^2`
`=(a-8)(a+8)`
`3, `
`8x^3-y^3`
`=(2x)^3-y^3`
`=(2x-y)(4x^2+2xy+y^2)`
`4, 25y^3-(1+4y)^2`
`=25y^3-(1+8y+16y^2)`
`=25y^3-1-8y-16y^2`
`5, (x+2)^2-(y+5)^2`
`=(x+2+y+5)(x+2-y-5)`
`=(x+y+7)(x+y-3)`
`6, (3-x)-(y-1)^2`
`=3-x-(y^2-2y+1)`
`=3-x-y^2+2y-1`
Xin hay nhất ạ