2x3-4x2+8x-2
(2x3-3x2+5x-1)-(x2+1-3x)
-3x+11y-13z
-2x3-10x2+9x+12
(4x+3y-8z)-(7x-8y+5z)
(8x2-2x+1)-(3x2+5x-8)
5x2-7x+9
(4x3+5x-7x2+9)-(6x3-4x+3x2-3)
