Bài 75:
c)
`(x+y)^3-x^3-y^3`
`=(x+y)^3-(x^3+y^3)`
`=(x+y)^3-(x+y)(x^2-xy+y^2)`
`=(x+y)(x+y)^2-(x+y)(x^2-xy+y^2)`
`=(x+y)[(x+y)^2-(x^2-xy+y^2)]`
`=(x+y)[(x^2+2xy+y^2)-(x^2-xy+y^2)]`
`=(x+y)[x^2+2xy+y^2-x^2+xy-y^2]`
`=(x+y)(3xy)`
d) Mk ko chắc bn tham khảo nhé :V
`5x^n+10x^(n+2)`
`=5.(x^n+2x^(n+2))`
$#Đã xin chủ tus r nhé$