а) 4b^2 - 2ab +2ab - a^2 = 4b^2 - a^2
б) c^2 - 3cd + 3cd - 9d^2 = c^2 - 9d^2
в) 6xy - y^2 + 36x^2 - 6xy = -y^2 + 36x^2
г) 6mn + 9m^2 - 4n^2 - 6mn = 9m^2 - 4n^2
1/(4b-a^2)
2/(c^2-9d)
3/-y^2+36^2
4/9m^2-4n^2
