2x (x - 7) - (x + 3)(x - 2) - (x + 4)(x - 4)

a)2x (x-7)-(x+3)(x-2)-(x+4)(x-4)
b)(x+2y)(x^2-2xy+4y^2)-(x-2y)(x^2+2xy+4y^2)+2y^3