Efectuati calculele :
a) (x + 2 )(x^2-x+3)-(x+1)(x^2+2x-5)
b) (2x+1)(x^2-2x+4)-(x-3)(2x^2+x+3)
c)(x-3)(x^2-3x+2)-(x+3)(x^2-2x+3)
d)(2x-1)(-x^2+x-2)+(2x-3)(x^2-x+1)