Ответ:

1.(x+y)^2=x^2+2xy+y^2

2.(x^2+xy+y^2)(xx-y)=x^3-y^3

3.(-x-y)^2=x^2+2xy+y^2

4.x^2-y^2=(x-y)(x+y)

5.y^2-x^2=(y-x)(y+x)

6.(k+m)^3=k^3+3k^m+3km^2+m^3

7.x^3-y^3=(x-y)(x^2+xy+y^2)

8.k^m+2km+m^2=(k+m)^2

9.x^2+2xy+y^2=(x+y)^2

10.-(x+y)^2=-x^2-2xy-y^2

11.(k-m)(k+m)=k^2-m^2

12.x^3-3x^2y+3xy^2-y^3=(x-y)^3

13.(-y+x)^2=x^2-2xy+y^2

14.(x-y)(x^2+xy-y^2)=x^3-2xy^2+y^3

15.x^2+y^2+z^2+2xy+2xz+2yz=(x+y+z)^2