Rút gọn: (2x -3y)^2 -(4x -6y+ 1)^2

1.Rút gọn
a,(x+1)^2+(x-2)^2-2x.(x+3)
b,(2x-3y)^2-(4x-6y+1)^2
c,(2x+y).(4x^2-2xy+y^2)-8x^3