A = (3x + y)^2 - 3y . ( 2x - 1/3y )

B = ( x - 2 )^2 + ( x + 2 )^2 - 2. ( x - 2 ) ( x + 2)

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

D = ( x -5 ) ( x+ 5 ) -(x - 8 ) (x + 4)

E = (3x + 1 )^2 - 2 . ( 9x^2 - 1 ) + ( 3x - 1 ) ^2

F = ( x - 3 ) ( x + 3 ) - ( x - 3 )^2