6xy-(x+3y)^2=
64m^2-49n^2=
25a^2+40ab+16b^2=
Помогите пожалуйста

6xy-(x^2+6xy+9y^2)=-x^2-9y^2=-(x^2+9y^2)=-(x+3y)(x+3y);

64m^2-49n^2=(8m-7n)(8m+7n);

25a^2+40ab+16b^2=(5a+4b)^2.