`a.(x^2+2xy+y^2):(x+y)`
`=(x+y)^2:(x+y)`
`=(x+y)(x+y):(x+y)`
`=x+y`
`b.(125x^3+1):(5x+1)`
`=[(5x)^3+1^3]:(5x+1)`
`=(5x+1)[(5x)^2-5x.1+1^2]:(5x+1)`
`=(25x^2-5x+1)(5x+1):(5x+1)`
`=25x^2-5x+1`
`c.(x^2-2xy+y^2):(x-y)`
`=(x-y)^2:(x-y)`
`=(x-y).(x-y):(x-y)`
`=x-y`
Áp dụng hằng đẳng thức:
`(a+b)^2=a^2+2ab+b^2`
`(a-b)^2=a^2-2ab+b^2`
`a^3+b^3=(a+b)(a^2-ab+b^2).`