(3x-2y+1)(3x+2y-1)=[3x-(2y-1)][3x+(2y-1)]=9x²-(2y-1)²=9x²-4y²+4y-1(3a-2)²-(3a+2)²=[(3a-2)-(3a+2)][(3a-2)+(3a+2)]=(3a-2-3-a-2)(3a-2+3a+2)=-4*6a=-24a