3x^4 + 3x^2y^2 + 6x^3y - 27x^2; x^4 + x^3 - x^2 + x; 2x^5 - 6x^4 - 2a^2x^3 - 6ax^3; x^5 + x^4 + x^3 + x^2 + x + 1; x^3 - 1 + 5x^2 - 5 + 3x - 3; 1/4.(a + 1)^2 - 4/9.(a - 2)^2

3x^4 + 3x^2y^2 + 6x^3y - 27x^2
x^4 + x^3 - x^2 + x
2x^5 - 6x^4 - 2a^2x^3 - 6ax^3
x^5 + x^4 + x^3 + x^2 + x + 1
x^3 - 1 + 5x^2 - 5 + 3x - 3
1/4.(a + 1)^2 - 4/9.(a - 2)^2
12a^2b^2 - 3.(a^2b^2)^2
4x^2y^2 - (x^2 + y^2 - a^2)^2
(a + b + c)^2 + (a + b - c)^2 - 4c^2
x^3 - 1 + 5x^2 - 5 + 3x - 3