soluzione Calcolare ( 1 x2-4y2-9+12y - 1 x2+4xy+4y2-9 ): x2 - 4y2 x2+6x-4y2+9 : 4y x+2y-3   =     =   ( 1 (x+2y-3)(x-2y+3) - 1 (x+2y-3)(x+2y+3) ): x2 - 4y2 x2+6x-4y2+9 : 4y x+2y-3   =     =   x+2y+3 -(x-2y+3) (x+2y-3)(x+2y+3)(x-2y+3) : x2 - 4y2 x2+6x-4y2+9 : 4y x+2y-3   =     =   x+2y+3 -x+2y-3 (x+2y-3)(x+2y+3)(x-2y+3) : x2 - 4y2 x2+6x-4y2+9 : 4y x+2y-3   =     =   4y (x+2y-3)(x+2y+3)(x-2y+3) : x2 - 4y2 x2+6x-4y2+9 : 4y x+2y-3   =     =   4y (x+2y-3)(x+2y+3)(x-2y+3) · x2+6x-4y2+9 x2 - 4y2 : 4y x+2y-3   =     =   4y (x+2y-3)(x+2y+3)(x-2y+3) · x2+6x-4y2+9 x2 - 4y2 · x+2y-3 4y   =     =   4y (x+2y-3)(x+2y+3)(x-2y+3) · (x-2y+3)(x+2y+3) (x - 2y)(x + 2y) · x+2y-3 4y   =     =   1 (x - 2y)(x + 2y)